Oceanography Glossary Definitions Flashcards

Terms Definitions
absolute dating
Determining the age of a geological sample by calculations of radioactive decay and/or its position in relation to other samples.
absorption
Conversion of sound or light energy into heat.
abyssal clay
lithogenous sediment on the deep-sea floor composed of at least 70% clay-sized particles by weight.
abyssal hill
Small sediment-covered inactive volcano or intrusion of molten rock less than 200 meters high, thought to be associated with sea-floor spreading. Abyssal hills punctuate the otherwise flat abyssal plain.
abyssal plain
Flat, cold, sediment-covered ocean floor between the continental rise and the mid-oceanic ridge at a depth of 3,700 to 5,300 meters. Abyssal plains are more extensive in the Atlantic and Indian Oceans than in the Pacific.
abyssal storm
Storm-like occurrences of rapid current movement affecting the deep ocean floor. They are believed to be caused by warm- and cold-core eddies of surface currents.
abyssal zone
The ocean between 13,120 and 19,680 feet deep.
abyssopelagic
Oceanic zone from 4000m to the deepest depth.
accessory pigment
One of the class of pigments (such as fucoxanthin, phycobilin, and xanthophyll) present in various photosynthetic plants and that assist in the absorption of light and the transfer of its energy to chlorophyll. Also called masking pigment.
accretion
An increase in the mass of a body by accumulation or a clumping of smaller particles.
acid
A substance that releases a hydrogen ion (H+) in solution.
acid rain
Rain containing acids and acid-forming compounds such as sulfur dioxide and oxides of nitrogen.
acoelomate
Without a secondary body cavity (coelom).
acoustic profiling
The use of seismic energy to measure sediment thickness and layering on the sea floor.
acoustic thermometry of ocean climate
ATOC; the measurement of ocean-wide changes in water properties such as temperature by transmitting and receiving low frequency sound signals.
acoustical tomography
A technique for studying ocean structure that depends on pulses of low frequency sounds to sense difference in water temperature, salinity, and movement beneath the surface.
action plan for the human environment
In 1972 this UN program established 12 worldwide environmental units and determined procedures for assessing and monitoring various sources of pollution.
active margin
Continental margin near an area of lithospheric plate convergence. Also called Pacific Type Margin.
active sonar
A device that generates underwater sound from special transducers and analyzes the returning echoes to gain information of geological, biological, or military importance.
active transport
The movement of molecules from a region of low concentration to a region of high concentration through a semipermeable membrane at the expense of energy.
adaptation
An inheritable structural or behavioral modification. A favorable adaptation gives a species an advantage in survival and reproduction. An unfavorable adaptation lessens a species ability to survive and reproduce.
adhesion
Attachment of water molecules to other substances of hydrogen bonds. Wetting.
adiabatic
Pertaining to a change in the temp of a mass resulting from compression or expansion; requires no addition of heat to or loss of heat from the substance.
adsorption
Attraction of ions to a solid surface.
advection
Horizontal or vertical transport of seawater, as by a current.
agar
Substance produced by red algae; the gelatin-like product of these algae.
Agnatha
The class of jawless fishes: hagfishes and lampreys.
ahermatypic
Describing coral species lacking symbiotic zooxanthellae and incapable of secreting calcium carbonate at a rate suitable for reef production.
air mass
A large mass of air with nearly uniform temperature, humidity, and density throughout.
Alaska gyre
A small Pacific Ocean subpolar surface current gyre that rotates counter-clockwise south of Alaska.
algae
Collective term for nonvascular plants possessing chlorophyll and capable of photosynthesis. Simple plants found as single cells or as seaweeds.
algin
A mucilaginous commercial product of multicellular marine algae. Widely used as a thickening and emulsifying agent.
Algulhas Current
A warm current that carries Indian Ocean water around the southern tip of Africa and into the Atlantic Ocean.
alkaline
Basic. See also base.
alluvial plain
A flat deposit of terrestrial sediment eroded by water from higher elevations.
alternation of generations
A reproductive cycle in which a plant alternates between sexual and asexual stages.
alveoli
A tiny thin-walled capillary rich sack in the lungs where the exchange of oxygen and carbon dioxide take place.
amnesic shellfish poisoning
Poisoning caused by demic acid secreted by a diatom. It has been known to kill birds and humans and obtains its name from the fact that the pervasive symptoms in humans is amnesia.
amphidromic point
A "no-tide" point in an ocean caused by basin resonances, friction, and other factors around which tide crests rotate. About a dozen amphidromic points exist in the world ocean. Also sometimes called a node.
anaerobic
Living or functioning in the absence of oxygen.
andesite
A volcanic rock intermediate in composition between basalt and granite; associated with subduction zones.
angiosperm
A flowering vascular plant that reproduces by means of a seed-bearing fruit. Examples are sea grasses and mangroves.
angle of incidence
In meteorology, the angle of the sun above the horizon.
animal
A multicellular organism unable to synthesize its own food and often capable of movement.
Animalia
The kingdom to which multicellular heterotrophs belong.
Annelida
The phylum of animals to which segmented worms belong.
anoxic
Deficient in oxygen.
Antarctic Bottom Water
The densest ocean water (1.0279 g/cm3), formed primarily in Antarctica's Weddell Sea during Southern Hemisphere winters.
Antarctic Circle
The line of latitude at 66°33'S marking the northern limit of the Antarctic region. The imaginary line around the Earth, parallel to the equator at 66°33'S, marking the southernmost limit of sunlight at the June solstice. The Antarctic Circle marks the northern limit of the area within which, for one day or more each year, the sun does not sea (around December 21) or rise (around June 21).
Antarctic Circumpolar Current
The current driven by powerful westerly winds north of Antarctica. The largest of all ocean currents, it continues permanently eastward without changing direction.
Antarctic Convergence
Convergence zone encircling Antarctica between about 50° and 60°S, marking the boundary between Antarctic Circumpolar Water and Subantarctic Surface Water.
Antarctic Ocean
An ocean in the Southern Hemisphere bounded to the north by the Atlantic Convergence and to the south by Antarctica.
antinode
Portion of a standing wave with maximum vertical motion.
aphelion
The point in the orbit of a satellite where it is farthest from the sun; opposite of perihelion.
aphotic zone
The part of the ocean where no surface light can penetrate.
apogean tide
A monthly tide of decreased range that occurs when the moon is farthest from earth (at apogee)
apogee
The point in the orbit of a satellite farthest from the main body; opposite of perigee.
aquaculture
The growing or farming of plants and animals in a water environment under controlled conditions. Compare mariculture.
Arctic Circle
The line of latitude at 66°33'N marking the southern limit of where the sun does not set in June or rise at December solstices.
Arctic Convergence
Convergence zone between Arctic Water and Subarctic Surface Water.
Arctic Ocean
An ice-covered ocean north of the continents of North America and Eurasia.
armored beach
A beach that is protected from wave and water erosion by coarse-size lag deposits.
Arthropoda
The phylum of animals that includes shrimp, lobsters, krill, barnacles, and insects. The phylum Arthropoda is the world's most successful.
artificial system of classification
A method of classifying an object based on attributes other than its reason for existence, its ancestry, or its origin. Compare natural system of classification.
ascidian
The sea squirts- a group of invertebrates that produce a larva with a primitive backbone.
aseimic ridge
see transverse ridge
Asteroidea
The class of the phylum Echinodermata to which sea stars belong.
asthenosphere
The hot, plastic layer of the upper mantle below the lithosphere, extending some 350 to 650 kilometers below the surface. Convection currents within the asthenosphere power plate tectonics.
astrolabe
An early navigation instrument that was the forerunner of the sextant.
atmospheric circulation cell
Large circuit of air driven by uneven solar heating and the Coriolis effect. Three circulation cells form in each hemisphere. See also Ferrel cell; Hadley cell; polar cell.
atmospheric pressure
Pressure, at any point on Earth, exerted by the atmosphere as a consequence of gravitational force exerted on the column of air lying directly above the point.
atoll
A ring-shaped island of coral reefs and coral debris enclosing, or almost enclosing, a central shallow lagoon from which no land protrudes. Atolls often form over sinking, inactive volcanoes.
atom
The smallest particle of an element that exhibits the characteristics of that element.
ATP
Adenosine triphosphate, the compound that acts as the immediate source of energy for all life on Earth. The energy stored in ATP is provided directly by photosynthesis or by respiration of glucose.
attenuation
Decrease in the energy of a wave or beam of particles occurring as the distance from the source increases; caused by absorption, scattering, and divergence from a point source.
authogenic sediment
Sediment formed directly by precipitation from seawater. Also called hydrogenous sediment.
autotroph
An organism that makes its own food by photosynthesis or chemosynthesis.
auxospore
A naked diatom cell without valves. Often a dormant stage in the life cycle following sexual reproduction.
Aves
The class of birds.
backshore
That part or zone of a beach profile that extends landward from the sloping foreshore to a point of either vegetation development or a change of physiography, e.g. a sea cliff or a dune field.
backshore
Sand on the shoreward side of the berm crest, sloping away from the ocean.
backwash
The water retreating down the shore after an incoming wave.
backwash
Water returning to the ocean from waves washing onto a beach.
bacteria
Single-celled prokaryotes, organisms lacking membrane-bound organelles.
Baguio
The local name given to tropical cyclones in the Philippines, especially those occurring from July to November.
Balearic Sea
One of the seas that comprise the western basin of the Mediterranean Sea which is sometimes called the Catalan Sea. It lies between The Iberian coast and the Balearic Islands (Ibiza, Mallorca, Menorca) in the northwestern Mediterranean.
baleen
The interleaved, hard, fibrous, hornlike filters within the mouth of baleen whales.
Bali Sea
A regional sea which is part of the Australasian Mediterranean Sea in the southwest Pacific Ocean. It is centered at around 116°E and 8.5°S and is bordered by Bali and Sumbawa to the south and Madura to the west.
Baltic Sea
A dilution basin type of Mediterranean sea that is connected to and experiences limited, intermittent water exchange with the North Sea.
bank
An undersea feature; and elevation of the sea floor, over which the depth of water is relatively shallow, but sufficient for safe surface navigation.
bar
Offshore ridge or mound of sand, gravel, or other loose material that is submerged, at least at high tide; located especially at the mouth of a river or estuary or lying a short distance from and parallel to the beach; A submerged or emerged mound of sand, gravel, or shell material built on the ocean floor in shallow water by waves and currents.
Barents Sea
One of the seas found on the Siberian shelf in the Arctic Mediterranean Sea. It is located between the White Sea to the west and the Kara Sea to the east and adjoins the Arctic Ocean proper to the north.
baroclinic
Descriptive of an atmosphere or ocean in which surfaces of pressure and density intersect at some level or levels. The state of the real atmosphere and ocean, as opposed to barotropic.
barotropic
Descriptive of a hypothetical atmosphere or ocean in which surfaces of pressure (isobaric surfaces) and density (isentropic surfaces) coincide at all levels, as compared to baroclinic. In a state of barotropic stratification, no potential energy is available for conversion to kinetic energy.
barrier island
A long, narrow, wave-built island lying parallel to the mainland and separated from it by a lagoon or bay. Compare sea island.
barrier layer
the layer between the thermocline and the halocline
barrier reef
One of three geomorphologically distinct types of coral reefs, the other two being fringing reefs and atolls. Barrier reefs are separated from land by a lagoon usually formed by coastal subsidence; A coral reef around islands or along continental coasts, with a deep lagoon between the reef and the coast.
barrier reef
A coral reef surrounding an island or lying parallel to the shore of a continent, separated from land by a deep lagoon. Coral debris islands may form along the reef.
barycenter
Center of mass and center rotation of the Earth-moon system, 1,700 kilometers inside Earth.
basalt
The relatively heavy crustal rock that forms the seabeds, composed mostly of oxygen, silicon, magnesium, and iron. Its density is about 2.9 g/cm3.
base
A substance that combines with a hydrogen ion (H+) in solution.
basin
An undersea feature; a depression, in the sea floor, more or less equidimensional in plan and of variable extent; large depression of the sea floor having about equal dimensions of length and width.
bathyal zone
The marine ecologic zone that lies deeper than the continental shelf but shallower than the deep ocean floor, i.e. those depths corresponding to the locations of the continental slope and rise.
bathyal zone
The ocean between about 200 and 4,000 meters deep.
bathybius
Thomas Henry Huxley's name for an artifact of marine specimen preservation he thought was a remnant of the "primeval living slime."
bathymetry
the measurement and charting of the spatial variation of the ocean depths.
bathymetry
The discovery and study of submerged contours.
bathypelagic zone
The ocean between 656 and 13,120 feet deep; One of five vertical ecological zones into which the deep sea is sometimes divided. This is the zone starting from 100 to 700 m deep (coinciding with the upper limit of the psychrosphere) at the 10°C isotherm.
bathyscaphe
Deep-diving submersible designed like a blimp, which uses gasoline for buoyancy and can reach the bottom of the deepest ocean trenches.
bathythermograph
A device developed by Athelstan Spilhaus in 1938 to measure temperature/depth profiles in the ocean. Replaced the oceanograph.
bay
A recess in the shore or an inlet of a sea between two capes or headlands, not as large as a gulf but larger than a cove.
bay mouth bar
An exposed sandbar attached to a headland adjacent to a bay and extending across the mouth of the bay.
Bay of Bengal
The northeastern arm of the Indian Ocean, located between India and Burma.
Bay of Nice
Located in the north western Mediterranean basin.
beach
The region of the shore where loose material, sand, mud, or pebble, are deposited between high- and low-water marks.
beach
A zone of unconsolidated (loose) particles extending from below water level to the edge of the coastal zone.
beach berm
The nearly horizontal portion of a beach formed by the deposition of sediment by receding waves. A beach may have more than one berm.
beach face
The sloping section of a beach profile below the beach berm which is normally exposed to the action of the wave swash.
beach scarp
Vertical wall of variable height marking the landward limit of the most recent high tides.
Beaufort scale
Scale of wind forces by range of velocity; scale of sea state created by winds of these velocities
Beaufort Sea
The marginal sea consisting of the waters off the northern coast of Alaska and Canada.
benthic
Descriptive of organisms that are attached to or resting on bottom sediments, as opposed to pelagic.
benthic zone
The seabed.
benthic zone
The zone of the ocean bottom. See also pelagic zone.
benthos
Organisms living on or in the ocean bottom.
Bering Sea
A marginal sea located on the northern rim of the Pacific Ocean centered at approximately 58°N and 160°W. It is surrounded by Alaska to the east, Siberia to the west, and the Aleutian Island arc to the south.
berm
A horizontal ridge of sand or shingle running parallel to the shore, at the limit of wave action.
berm
A nearly horizontal accumulation of sediment parallel to shore. Marks the normal limit of sand deposition by wave action.
berm crest
The seaward limit of a beach berm.
berm crest
The top of the berm, the highest point on most beaches. Corresponds to the shoreward limit of wave action during most high tides.
beta refraction
An effect that results from the latitudinal variation of Rossby wave phase speed which is, in turn, due to the beta effect. If a line of Rossby waves were started along a straight eastern ocean boundary, then those at low latitudes would arrive at the western boundary before those at high latitudes.
bias
The amount by which the average of a set of values departs from a reference value.
big bang
The hypothetical event that started the expansion of the universe from a geometric point. The beginning of time.
bilateral symmetry
Body structure having left and right sides that are approximate mirror images of each other. Examples are crabs and humans. Compare radial symmetry.
biodegradable
Able to be broken by natural processes into simpler compounds.
biodiversity
The variety of different species within a habitat.
biogenic
One of three major components of deep sea sediments, the other two being authigenic and detrital. Biogenic sediment consists mainly of calcite and opal produced as the hard parts of organisms and eventually precipitated.
biogenous sediment
Sediment of biological origin. Organisms can deposit calcareous (calcium-containing) or siliceous (silicon-containing) residue.
biogeochemical sediment
Natural processes that recycle nutrients in various chemical forms from the nonliving environment to the living organisms and then back to the nonliving environment.
biological amplification
Increase in concentration of certain fat-soluble chemicals such as DDT or heavy metal compounds, in successively higher trophic levels within a food web.
biological factor
A biologically generated aspect of the environment, such as predation or metabolic waste products, that affects living organisms. Biological factors usually operate in association with purely physical factors such as light and temperature.
biological pump
Photosynthetic transfer of carbon as CO2 from the atmosphere to the ocean in the form of organic molecules; carbon is transferred to intermediate and deep-ocean water when organic material sinks and decays.
biological resource
A living animal or plant collected for human use. Also called a living resource.
bioluminescence
The generation of light by living organisms using the enzyme luciferase.
bioluminescence
Biologically produced light.
biomass
The mass of living material in a given area or volume of habitat.
biosynthesis
The initial formation of life on Earth.
bioturbation
The stirring of sediment by animal life.
bioturbation
Reworking of sediments by organisms that burrow into them and ingest them.
Bivalvia
The class of phylum Mollusca that includes clams, oysters, and mussels.
Bjerknes, Vilhelm
(1862-1951) Pioneering Norwegian physicist and discoverer of the nature and formation of extratropical cyclones, which cause most mid-latitude weather.
Black Sea
A Mediterranean sea, centered at approximately 35°E and 44°N, that is the world's largest inland water basin.
Blade
Algal equivalent of a vascular plant's leaf. Also called a frond.
bloom
The sudden increase in phytoplankton number, usually associated with season changes.
bloom
High concentration of phytoplankton in an area, caused by increased reproduction; often produces discoloration of water. See red tide.
Bohol Sea
A small sea centered in the Philippines at about 124°E and 9°S.
bond
An energy relationship that holds two atoms together as a result of changes in their electron distribution.
borderland
undersea feature; a region adjacent to a continent, normally occupied by or bordering a shelf and sometimes emerging as islands.
Bowen ration
The ratio of the amount of sensible to that of latent heat lost by a surface to the atmosphere by the processes of conduction and turbulence.
brackish
Describing water intermediate in salinity between seawater and freshwater.
Bransfield Strait
A strait located between the northern tip of the Antarctica Peninsula and the South Shetland Islands. 120 km wide and extends 460 km from Clarence Island to Low Island.
brash ice
A type of sea ice; accumulations of floating ice made up of fragments not more than 2 meters across; the wreckage of other forms of ice.
Brazil Basin
An ocean basin located off the eastern coast of Brazil in the west-central Atlantic Ocean.
breaker
Sea surface water wave that has become too steep to be stable and collapses.
breaker zone
The portion of the nearshore zone where waves arriving from offshore become unstable and break
breakwater
Structure protecting a shore area, harbor, anchorage, or basin from waves; a type of jetty.
breakwater
An artificial structure of durable material that interrupts the progress of waves to shore. Harbors are often shielded by breakwater.
bucket temperature
The surface temperature of the ocean as measured by a bucket thermometer.
bucket thermometer
A thermometer with an insulated container around the bulb.
buffer
A group of substances that tends to resist change in the pH of a solution by combining with free ions.
buffer factor
Defined as the fractional changed in atmospheric CO2 divided by the fractional change in oceanic DIC after equilibrium has been reached.
buffer sublayer
That part of a boundary layer where the viscous stress and the Reynolds stress have the same order of magnitude and the linear velocity profile turns smoothly into the logarithmic profile.
bulkhead
Structure separating land and water areas; primarily designed to resist earth sliding and slumping or to reduce wave erosion at the base of a cliff.
buoy
Floating object to float due to the support of the fluid the body is in or on.
buoyancy
The ability of an object to float in a fluid by displacement of a volume of fluid equal to it in mass.
by-catch
See incidental catch.
bykill
Animals unintentionally killed when desirable organisms are collected.
caballing
Mixing of two water masses of identical densities but different temperatures and salinities, such that the resulting mixture is denser than its components.
cabbeling
A phenomenon that occurs when two water masses with identical densities but different temperatures and salinities mix to form a third water mass with a greater density than either of its constituents.
calcareous
Of or containing calcium carbonate or another, usually insoluble, calcium salt.
absolute dating
Determining the age of a geological sample by calculations of radioactive decay and/or its position in relation to other samples.
absorption
Conversion of sound or light energy into heat.
abyssal clay
lithogenous sediment on the deep-sea floor composed of at least 70% clay-sized particles by weight.
abyssal hill
Small sediment-covered inactive volcano or intrusion of molten rock less than 200 meters high, thought to be associated with sea-floor spreading. Abyssal hills punctuate the otherwise flat abyssal plain.
abyssal plain
Flat, cold, sediment-covered ocean floor between the continental rise and the mid-oceanic ridge at a depth of 3,700 to 5,300 meters. Abyssal plains are more extensive in the Atlantic and Indian Oceans than in the Pacific.
abyssal storm
Storm-like occurrences of rapid current movement affecting the deep ocean floor. They are believed to be caused by warm- and cold-core eddies of surface currents.
abyssal zone
The ocean between 13,120 and 19,680 feet deep.
abyssopelagic
Oceanic zone from 4000m to the deepest depth.
accessory pigment
One of the class of pigments (such as fucoxanthin, phycobilin, and xanthophyll) present in various photosynthetic plants and that assist in the absorption of light and the transfer of its energy to chlorophyll. Also called masking pigment.
accretion
An increase in the mass of a body by accumulation or a clumping of smaller particles.
acid
A substance that releases a hydrogen ion (H+) in solution.
acid rain
Rain containing acids and acid-forming compounds such as sulfur dioxide and oxides of nitrogen.
acoelomate
Without a secondary body cavity (coelom).
acoustic profiling
The use of seismic energy to measure sediment thickness and layering on the sea floor.
acoustic thermometry of ocean climate
ATOC; the measurement of ocean-wide changes in water properties such as temperature by transmitting and receiving low frequency sound signals.
acoustical tomography
A technique for studying ocean structure that depends on pulses of low frequency sounds to sense difference in water temperature, salinity, and movement beneath the surface.
action plan for the human environment
In 1972 this UN program established 12 worldwide environmental units and determined procedures for assessing and monitoring various sources of pollution.
active margin
Continental margin near an area of lithospheric plate convergence. Also called Pacific Type Margin.
active sonar
A device that generates underwater sound from special transducers and analyzes the returning echoes to gain information of geological, biological, or military importance.
active transport
The movement of molecules from a region of low concentration to a region of high concentration through a semipermeable membrane at the expense of energy.
adaptation
An inheritable structural or behavioral modification. A favorable adaptation gives a species an advantage in survival and reproduction. An unfavorable adaptation lessens a species ability to survive and reproduce.
adhesion
Attachment of water molecules to other substances of hydrogen bonds. Wetting.
adiabatic
Pertaining to a change in the temp of a mass resulting from compression or expansion; requires no addition of heat to or loss of heat from the substance.
adsorption
Attraction of ions to a solid surface.
advection
Horizontal or vertical transport of seawater, as by a current.
agar
Substance produced by red algae; the gelatin-like product of these algae.
Agnatha
The class of jawless fishes: hagfishes and lampreys.
ahermatypic
Describing coral species lacking symbiotic zooxanthellae and incapable of secreting calcium carbonate at a rate suitable for reef production.
air mass
A large mass of air with nearly uniform temperature, humidity, and density throughout.
Alaska gyre
A small Pacific Ocean subpolar surface current gyre that rotates counter-clockwise south of Alaska.
algae
Collective term for nonvascular plants possessing chlorophyll and capable of photosynthesis. Simple plants found as single cells or as seaweeds.
algin
A mucilaginous commercial product of multicellular marine algae. Widely used as a thickening and emulsifying agent.
Algulhas Current
A warm current that carries Indian Ocean water around the southern tip of Africa and into the Atlantic Ocean.
alkaline
Basic. See also base.
alluvial plain
A flat deposit of terrestrial sediment eroded by water from higher elevations.
alternation of generations
A reproductive cycle in which a plant alternates between sexual and asexual stages.
alveoli
A tiny thin-walled capillary rich sack in the lungs where the exchange of oxygen and carbon dioxide take place.
amnesic shellfish poisoning
Poisoning caused by demic acid secreted by a diatom. It has been known to kill birds and humans and obtains its name from the fact that the pervasive symptoms in humans is amnesia.
amphidromic point
A "no-tide" point in an ocean caused by basin resonances, friction, and other factors around which tide crests rotate. About a dozen amphidromic points exist in the world ocean. Also sometimes called a node.
anaerobic
Living or functioning in the absence of oxygen.
andesite
A volcanic rock intermediate in composition between basalt and granite; associated with subduction zones.
angiosperm
A flowering vascular plant that reproduces by means of a seed-bearing fruit. Examples are sea grasses and mangroves.
angle of incidence
In meteorology, the angle of the sun above the horizon.
animal
A multicellular organism unable to synthesize its own food and often capable of movement.
Animalia
The kingdom to which multicellular heterotrophs belong.
Annelida
The phylum of animals to which segmented worms belong.
anoxic
Deficient in oxygen.
Antarctic Bottom Water
The densest ocean water (1.0279 g/cm3), formed primarily in Antarctica's Weddell Sea during Southern Hemisphere winters.
Antarctic Circle
The line of latitude at 66°33'S marking the northern limit of the Antarctic region. The imaginary line around the Earth, parallel to the equator at 66°33'S, marking the southernmost limit of sunlight at the June solstice. The Antarctic Circle marks the northern limit of the area within which, for one day or more each year, the sun does not sea (around December 21) or rise (around June 21).
Antarctic Circumpolar Current
The current driven by powerful westerly winds north of Antarctica. The largest of all ocean currents, it continues permanently eastward without changing direction.
Antarctic Convergence
Convergence zone encircling Antarctica between about 50° and 60°S, marking the boundary between Antarctic Circumpolar Water and Subantarctic Surface Water.
Antarctic Ocean
An ocean in the Southern Hemisphere bounded to the north by the Atlantic Convergence and to the south by Antarctica.
antinode
Portion of a standing wave with maximum vertical motion.
aphelion
The point in the orbit of a satellite where it is farthest from the sun; opposite of perihelion.
aphotic zone
The part of the ocean where no surface light can penetrate.
apogean tide
A monthly tide of decreased range that occurs when the moon is farthest from earth (at apogee)
apogee
The point in the orbit of a satellite farthest from the main body; opposite of perigee.
aquaculture
The growing or farming of plants and animals in a water environment under controlled conditions. Compare mariculture.
Arctic Circle
The line of latitude at 66°33'N marking the southern limit of where the sun does not set in June or rise at December solstices.
Arctic Convergence
Convergence zone between Arctic Water and Subarctic Surface Water.
Arctic Ocean
An ice-covered ocean north of the continents of North America and Eurasia.
armored beach
A beach that is protected from wave and water erosion by coarse-size lag deposits.
Arthropoda
The phylum of animals that includes shrimp, lobsters, krill, barnacles, and insects. The phylum Arthropoda is the world's most successful.
artificial system of classification
A method of classifying an object based on attributes other than its reason for existence, its ancestry, or its origin. Compare natural system of classification.
ascidian
The sea squirts- a group of invertebrates that produce a larva with a primitive backbone.
aseimic ridge
see transverse ridge
Asteroidea
The class of the phylum Echinodermata to which sea stars belong.
asthenosphere
The hot, plastic layer of the upper mantle below the lithosphere, extending some 350 to 650 kilometers below the surface. Convection currents within the asthenosphere power plate tectonics.
astrolabe
An early navigation instrument that was the forerunner of the sextant.
atmospheric circulation cell
Large circuit of air driven by uneven solar heating and the Coriolis effect. Three circulation cells form in each hemisphere. See also Ferrel cell; Hadley cell; polar cell.
atmospheric pressure
Pressure, at any point on Earth, exerted by the atmosphere as a consequence of gravitational force exerted on the column of air lying directly above the point.
atoll
A ring-shaped island of coral reefs and coral debris enclosing, or almost enclosing, a central shallow lagoon from which no land protrudes. Atolls often form over sinking, inactive volcanoes.
atom
The smallest particle of an element that exhibits the characteristics of that element.
ATP
Adenosine triphosphate, the compound that acts as the immediate source of energy for all life on Earth. The energy stored in ATP is provided directly by photosynthesis or by respiration of glucose.
attenuation
Decrease in the energy of a wave or beam of particles occurring as the distance from the source increases; caused by absorption, scattering, and divergence from a point source.
authogenic sediment
Sediment formed directly by precipitation from seawater. Also called hydrogenous sediment.
autotroph
An organism that makes its own food by photosynthesis or chemosynthesis.
auxospore
A naked diatom cell without valves. Often a dormant stage in the life cycle following sexual reproduction.
Aves
The class of birds.
backshore
That part or zone of a beach profile that extends landward from the sloping foreshore to a point of either vegetation development or a change of physiography, e.g. a sea cliff or a dune field.
backshore
Sand on the shoreward side of the berm crest, sloping away from the ocean.
backwash
The water retreating down the shore after an incoming wave.
backwash
Water returning to the ocean from waves washing onto a beach.
bacteria
Single-celled prokaryotes, organisms lacking membrane-bound organelles.
Baguio
The local name given to tropical cyclones in the Philippines, especially those occurring from July to November.
Balearic Sea
One of the seas that comprise the western basin of the Mediterranean Sea which is sometimes called the Catalan Sea. It lies between The Iberian coast and the Balearic Islands (Ibiza, Mallorca, Menorca) in the northwestern Mediterranean.
baleen
The interleaved, hard, fibrous, hornlike filters within the mouth of baleen whales.
Bali Sea
A regional sea which is part of the Australasian Mediterranean Sea in the southwest Pacific Ocean. It is centered at around 116°E and 8.5°S and is bordered by Bali and Sumbawa to the south and Madura to the west.
Baltic Sea
A dilution basin type of Mediterranean sea that is connected to and experiences limited, intermittent water exchange with the North Sea.
bank
An undersea feature; and elevation of the sea floor, over which the depth of water is relatively shallow, but sufficient for safe surface navigation.
bar
Offshore ridge or mound of sand, gravel, or other loose material that is submerged, at least at high tide; located especially at the mouth of a river or estuary or lying a short distance from and parallel to the beach; A submerged or emerged mound of sand, gravel, or shell material built on the ocean floor in shallow water by waves and currents.
Barents Sea
One of the seas found on the Siberian shelf in the Arctic Mediterranean Sea. It is located between the White Sea to the west and the Kara Sea to the east and adjoins the Arctic Ocean proper to the north.
baroclinic
Descriptive of an atmosphere or ocean in which surfaces of pressure and density intersect at some level or levels. The state of the real atmosphere and ocean, as opposed to barotropic.
barotropic
Descriptive of a hypothetical atmosphere or ocean in which surfaces of pressure (isobaric surfaces) and density (isentropic surfaces) coincide at all levels, as compared to baroclinic. In a state of barotropic stratification, no potential energy is available for conversion to kinetic energy.
barrier island
A long, narrow, wave-built island lying parallel to the mainland and separated from it by a lagoon or bay. Compare sea island.
barrier layer
the layer between the thermocline and the halocline
barrier reef
One of three geomorphologically distinct types of coral reefs, the other two being fringing reefs and atolls. Barrier reefs are separated from land by a lagoon usually formed by coastal subsidence; A coral reef around islands or along continental coasts, with a deep lagoon between the reef and the coast.
barrier reef
A coral reef surrounding an island or lying parallel to the shore of a continent, separated from land by a deep lagoon. Coral debris islands may form along the reef.
barycenter
Center of mass and center rotation of the Earth-moon system, 1,700 kilometers inside Earth.
basalt
The relatively heavy crustal rock that forms the seabeds, composed mostly of oxygen, silicon, magnesium, and iron. Its density is about 2.9 g/cm3.
base
A substance that combines with a hydrogen ion (H+) in solution.
basin
An undersea feature; a depression, in the sea floor, more or less equidimensional in plan and of variable extent; large depression of the sea floor having about equal dimensions of length and width.
bathyal zone
The marine ecologic zone that lies deeper than the continental shelf but shallower than the deep ocean floor, i.e. those depths corresponding to the locations of the continental slope and rise.
bathyal zone
The ocean between about 200 and 4,000 meters deep.
bathybius
Thomas Henry Huxley's name for an artifact of marine specimen preservation he thought was a remnant of the "primeval living slime."
bathymetry
the measurement and charting of the spatial variation of the ocean depths.
bathymetry
The discovery and study of submerged contours.
bathypelagic zone
The ocean between 656 and 13,120 feet deep; One of five vertical ecological zones into which the deep sea is sometimes divided. This is the zone starting from 100 to 700 m deep (coinciding with the upper limit of the psychrosphere) at the 10°C isotherm.
bathyscaphe
Deep-diving submersible designed like a blimp, which uses gasoline for buoyancy and can reach the bottom of the deepest ocean trenches.
bathythermograph
A device developed by Athelstan Spilhaus in 1938 to measure temperature/depth profiles in the ocean. Replaced the oceanograph.
bay
A recess in the shore or an inlet of a sea between two capes or headlands, not as large as a gulf but larger than a cove.
bay mouth bar
An exposed sandbar attached to a headland adjacent to a bay and extending across the mouth of the bay.
Bay of Bengal
The northeastern arm of the Indian Ocean, located between India and Burma.
Bay of Nice
Located in the north western Mediterranean basin.
beach
The region of the shore where loose material, sand, mud, or pebble, are deposited between high- and low-water marks.
beach
A zone of unconsolidated (loose) particles extending from below water level to the edge of the coastal zone.
beach berm
The nearly horizontal portion of a beach formed by the deposition of sediment by receding waves. A beach may have more than one berm.
beach face
The sloping section of a beach profile below the beach berm which is normally exposed to the action of the wave swash.
beach scarp
Vertical wall of variable height marking the landward limit of the most recent high tides.
Beaufort scale
Scale of wind forces by range of velocity; scale of sea state created by winds of these velocities
Beaufort Sea
The marginal sea consisting of the waters off the northern coast of Alaska and Canada.
benthic
Descriptive of organisms that are attached to or resting on bottom sediments, as opposed to pelagic.
benthic zone
The seabed.
benthic zone
The zone of the ocean bottom. See also pelagic zone.
benthos
Organisms living on or in the ocean bottom.
Bering Sea
A marginal sea located on the northern rim of the Pacific Ocean centered at approximately 58°N and 160°W. It is surrounded by Alaska to the east, Siberia to the west, and the Aleutian Island arc to the south.
berm
A horizontal ridge of sand or shingle running parallel to the shore, at the limit of wave action.
berm
A nearly horizontal accumulation of sediment parallel to shore. Marks the normal limit of sand deposition by wave action.
berm crest
The seaward limit of a beach berm.
berm crest
The top of the berm, the highest point on most beaches. Corresponds to the shoreward limit of wave action during most high tides.
beta refraction
An effect that results from the latitudinal variation of Rossby wave phase speed which is, in turn, due to the beta effect. If a line of Rossby waves were started along a straight eastern ocean boundary, then those at low latitudes would arrive at the western boundary before those at high latitudes.
bias
The amount by which the average of a set of values departs from a reference value.
big bang
The hypothetical event that started the expansion of the universe from a geometric point. The beginning of time.
bilateral symmetry
Body structure having left and right sides that are approximate mirror images of each other. Examples are crabs and humans. Compare radial symmetry.
biodegradable
Able to be broken by natural processes into simpler compounds.
biodiversity
The variety of different species within a habitat.
biogenic
One of three major components of deep sea sediments, the other two being authigenic and detrital. Biogenic sediment consists mainly of calcite and opal produced as the hard parts of organisms and eventually precipitated.
biogenous sediment
Sediment of biological origin. Organisms can deposit calcareous (calcium-containing) or siliceous (silicon-containing) residue.
biogeochemical sediment
Natural processes that recycle nutrients in various chemical forms from the nonliving environment to the living organisms and then back to the nonliving environment.
biological amplification
Increase in concentration of certain fat-soluble chemicals such as DDT or heavy metal compounds, in successively higher trophic levels within a food web.
biological factor
A biologically generated aspect of the environment, such as predation or metabolic waste products, that affects living organisms. Biological factors usually operate in association with purely physical factors such as light and temperature.
biological pump
Photosynthetic transfer of carbon as CO2 from the atmosphere to the ocean in the form of organic molecules; carbon is transferred to intermediate and deep-ocean water when organic material sinks and decays.
biological resource
A living animal or plant collected for human use. Also called a living resource.
bioluminescence
The generation of light by living organisms using the enzyme luciferase.
bioluminescence
Biologically produced light.
biomass
The mass of living material in a given area or volume of habitat.
biosynthesis
The initial formation of life on Earth.
bioturbation
The stirring of sediment by animal life.
bioturbation
Reworking of sediments by organisms that burrow into them and ingest them.
Bivalvia
The class of phylum Mollusca that includes clams, oysters, and mussels.
Bjerknes, Vilhelm
(1862-1951) Pioneering Norwegian physicist and discoverer of the nature and formation of extratropical cyclones, which cause most mid-latitude weather.
Black Sea
A Mediterranean sea, centered at approximately 35°E and 44°N, that is the world's largest inland water basin.
Blade
Algal equivalent of a vascular plant's leaf. Also called a frond.
bloom
The sudden increase in phytoplankton number, usually associated with season changes.
bloom
High concentration of phytoplankton in an area, caused by increased reproduction; often produces discoloration of water. See red tide.
Bohol Sea
A small sea centered in the Philippines at about 124°E and 9°S.
bond
An energy relationship that holds two atoms together as a result of changes in their electron distribution.
borderland
undersea feature; a region adjacent to a continent, normally occupied by or bordering a shelf and sometimes emerging as islands.
Bowen ration
The ratio of the amount of sensible to that of latent heat lost by a surface to the atmosphere by the processes of conduction and turbulence.
brackish
Describing water intermediate in salinity between seawater and freshwater.
Bransfield Strait
A strait located between the northern tip of the Antarctica Peninsula and the South Shetland Islands. 120 km wide and extends 460 km from Clarence Island to Low Island.
brash ice
A type of sea ice; accumulations of floating ice made up of fragments not more than 2 meters across; the wreckage of other forms of ice.
Brazil Basin
An ocean basin located off the eastern coast of Brazil in the west-central Atlantic Ocean.
breaker
Sea surface water wave that has become too steep to be stable and collapses.
breaker zone
The portion of the nearshore zone where waves arriving from offshore become unstable and break
breakwater
Structure protecting a shore area, harbor, anchorage, or basin from waves; a type of jetty.
breakwater
An artificial structure of durable material that interrupts the progress of waves to shore. Harbors are often shielded by breakwater.
bucket temperature
The surface temperature of the ocean as measured by a bucket thermometer.
bucket thermometer
A thermometer with an insulated container around the bulb.
buffer
A group of substances that tends to resist change in the pH of a solution by combining with free ions.
buffer factor
Defined as the fractional changed in atmospheric CO2 divided by the fractional change in oceanic DIC after equilibrium has been reached.
buffer sublayer
That part of a boundary layer where the viscous stress and the Reynolds stress have the same order of magnitude and the linear velocity profile turns smoothly into the logarithmic profile.
bulkhead
Structure separating land and water areas; primarily designed to resist earth sliding and slumping or to reduce wave erosion at the base of a cliff.
buoy
Floating object to float due to the support of the fluid the body is in or on.
buoyancy
The ability of an object to float in a fluid by displacement of a volume of fluid equal to it in mass.
by-catch
See incidental catch.
bykill
Animals unintentionally killed when desirable organisms are collected.
caballing
Mixing of two water masses of identical densities but different temperatures and salinities, such that the resulting mixture is denser than its components.
cabbeling
A phenomenon that occurs when two water masses with identical densities but different temperatures and salinities mix to form a third water mass with a greater density than either of its constituents.
calcareous
Of or containing calcium carbonate or another, usually insoluble, calcium salt.
calcareous ooze
Partially composed organic matter mixed with a quantity of calcareous material on the bottom of some bodies of water; a fine-grained, deep-sea deposit of pelagic origin containing more than 30% calcium carbonate derived from the skeletal material of various plankton. It is the most extensive deposit on the ocean floor but restricted to depths less than about 3500 m due to the carbon compensation depth.
calcareous ooze
Ooze composed mostly of the hard remains of organisms containing calcium carbonate.
calcium carbonate compensation depth
The depth at which the rate of accumulation of calcareous sediments equals the rate of dissolution of those sediments. Below this depth, sediment contains little or no calcium carbonate.
caldera
undersea feature; a collapsed or partially-collapsed seamount, commonly of annular shape.
calorie
The amount of heat needed to raise the temperatures of 1 gram (0.035 ounce) of pure water by 1°C (1.8°F).
calving
Breaking away of a mass of ice from its parent glacier, iceberg, or sea ice formation.
Camotes Sea
A small sea within the Visayan Islands that comprise the middle portion of the Philippines.
Canary Basin
An ocean basin located to the west of the Canary Islands in the eastern North Atlantic Ocean.
canyon
Undersea feature; a relatively narrow, deep depression with steep sides, the bottom of which generally deepends continuously, developed characteristically on some continental slopes.
Cape Basin
An ocean basin located to the west of South Africa at about 35°S in the South Atlantic Ocean.
Cape Verde Basin
An ocean basin located at about 15°N off the west coast of Africa in the North Atlantic Ocean.
capillary wave
A wave on a fluid interface for which the restoring force is surface tension.
capillary wave
A tiny wave with a wavelength of less than 1.73 centimeters (0.68 inch), whose restoring force is surface tension; the first type of wave to form when the wind blows.
carbon cycle
The cycling of carbon in the form of carbon dioxide, carbonates, organic compounds, etc. between various reservoirs, e.g. the atmosphere, the oceans, land and marine biota and, on geological time scales, sediments, and rocks.
carbon dioxide
The most important of the greenhouse gases with an atmospheric concentration of 353 ppm.
carbon-14 dating
A radioisotope dating method wherein a radioactive isotope of carbon, also called radiocarbon, is used to date materials containing carbon.
carbonate compensation depth
(CCD) Also known as the calcite compensation depth, is the depth at which the amount of calcium carbonate preserved falls below 20% of the total sediment. This is also commonly defined as the depth at which the amount of calcium carbonate produced by organisms skeletal material in the overlying water column is equal to the rate at which it is dissolved in the water. No calcium carbonate will be deposited below this depth.
Cariaco Basin
A 1400 m deep depression within the continental shelf of Venezuela.
Caribbean Sea
The largest marginal sea of the Atlantic Ocean, with a surface area twice that of the Mediterranean Sea.
Carnivora
The order of mammals that includes seals, sea lions, walruses, and sea otters.
carrageenan
Substance produced by certain algae that acts as a thickening agent.
carrying capacity
The size at which a particular population in a particular environment will stabilize when its supply of resources--including nutrients, energy and living space -- remains constant.
cartilage
A tough, elastic tissue that stiffens or supports.
cartographer
A person who makes maps and charts.
Catalan Sea
See Balearic Sea
catastrophism
The theory that the Earth's surface features are formed by catastrophic forces such as the biblical flood. Catastrophists believe in a young Earth and a literal interpretation of the biblical account of Creation.
cat's-paw
Patch of ripples on the water's surface, related to a discrete gust of wind.
Celebes Sea
Alternate name for the Sulawesi Sea.
celestial navigation
The technique of finding one's position on Earth by reference to the apparent position of stars, planets, the moon, and the sun.
cell
The basic organizational unit of life on this planet.
Celtic Sea
A shallow embayment of the eastern North Atlantic bounded by Southern Ireland. Separated from the Irish Sea by a line drawn from Ramsey Island to Carnsore Point and from the English Channel by a line drawn from Ushant to Lands End.
Cenderawasih Bay
A bay on the northern coast of Irian Jaya centered at approximately 135°E and 2.5°S at the southwestern edge of the Pacific Ocean.
centers of action
Large semi permanent belts of high or low sea level pressure distributed around the Earth that largely control the general circulation of the atmosphere and the concomitant long-term weather patterns.
central water
A term used to identify thermocline water masses in all three oceans. The water arrives at a thermocline via a process known as subduction.
centrifugal force
Outward-directed force acting on a body moving along a curved path or rotating about an axis; an inertial force.
cephalopod
An advanced group of mollusks that includes the squids, octopuses, and cuttlefishes.
Cephalopoda
The class of the phylum Mollusca that includes squid, octopuses, and nautiluses.
cetacea
The order of mammals that includes porpoises, dolphins and whales.
cetaceans
The whales and dolphins.
CFCs
A class of halogenated hydrocarbons thought to be depleting Earth's atmospheric ozone. CFCs are used as cleaning agents, refrigerants, fire extinguishing fluids, spray can propellants, and insulating foams.
chaetognaths
Free-swimming, carnivorous, pelagic, wormlike, planktonic animals; arrowworms.
Challenger Expedition
The first wholly scientific oceanographic expedition, 1872-76. Named for the steam corvette used in the voyage.
channel
A body of water that connects two larger bodies of water. A channel is also part of a river or harbor that is deep enough to let ships sail through.
chart
A map that depicts mostly water and the adjoining land areas.
chemical bond
An energy relationship that holds two atoms together as a result of changes in their electron distribution.
chemical equilibrium
In seawater, the condition in which the proportion and amounts of dissolved salts per unit volume of ocean are nearly consistent.
chemosynthesis
The synthesis of organic compounds from inorganic compounds using energy stored in inorganic substances such as sulfur, ammonia, and hydrogen. Energy is released when these substances are oxidized by certain organisms.
chitin
A complex nitrogen-rich carbohydrate from which parts of arthropod exoskeletons are constructed.
chiton
A polyplasophoran mollusk.
chlorinated hydrocarbons
The most abundant and dangerous class of halogenated hydrocarbons, synthetic organic chemicals hazardous to the marine environment.
chlorine titration
The method developed by Knudsen in 1902 to determine the chlorinity and therefore salinity of a sea water sample.
chlorinity
A measure of the amount of chlorine or other halides in water (especially seawater).
chlorinity
A measure of the content of chloride, bromine, and iodide ions in seawater. We may derive salinity from chlorinity by multiplying by 1.80655.
chlorofluorocarbons
A class of halogenated hydrocarbons thought to be depleting Earth's atmospheric ozone. CFCs are used as cleaning agents, refrigerants, fire extinguishing fluids, spray can propellants, and insulating foams.
chlorophyll
A pigment responsible for trapping sunlight and transferring its energy to electrons, thus initiating photosynthesis.
Chlorophyta
Green algae.
Chondrichthyes
The class of fishes with cartilagenous skeletons: the sharks, skates, rays, and chimaeras.
Chordata
The phylum of animals to which tunicates, Amphioxus, fishes, amphibians, reptiles, birds, and mammals belong.
chromatophore
A pigmented skin cell that expands or contracts to affect color change.
chronometer
A watch or clock able to maintain its accuracy on long sea voyages.
chronometer
A very consistent clock. It doesn't need to tell accurate time, but its rate of gain or loss must be constant and known exactly so that accurate time may be calculated.
ciguatera
Toxin found in fish of tropical regions; produced by dinoflagellates.
cilia
Microscopic, hairlike projections of living cells that beat in coordinated fashion and produce movement.
clamshell sampler
Sampling device used to take shallow samples of the ocean bottom.
classification
A way of grouping objects according to some stated criteria.
clay
Sediment particle smaller than 0.004mm in diameter; the smallest sediment size category.
climate
The long-term average of weather in an area.
climax community
A stable, long-established community of self-perpetuating organisms that tends not to change with time.
clockwise
Rotation around a point in the direction that clock hands move.
clumped distribution
Distribution of organisms within a community in small, patchy aggregations, or clumps; the most common distribution pattern.
Cnidaria
The phylum of animals to which corals, jellyfish, and sea anemones belong.
cnidoblast
Type of cell found in members of the phylum Cnidaria that contains a stinging capsule. The threads that evert from the capsules assist in capturing prey and repelling aggressors.
coast
The zone extending from the ocean inland as far as the environment is immediately affected by marine processes.
coastal cell
The natural sector of a coastline in which sand input and sand outflow are balanced.
coastal upwelling
Upwelling adjacent to a coast, usually induced by wind.
coccolithophore
A very small planktonic alga carrying discs of calcium carbonate, which contributes to biogenous sediments.
cohesion
Attachment of water molecules to each other by hydrogen bonds.
cold seep
Cold seawater, rich in methane, hydrogen sulfide, and hydrocarbons issuing from the seafloor.
colligative properties
Those characteristics of a solution that differ from those of pure water because of material held in solution.
Columbus, Christopher
1451-1506. Italian explorer in the service of Spain who discovered islands in the Caribbean in 1492. Although traditionally credited as the discoverer of America, he never actually sighted the North American continent.
commensalism
A symbiotic interaction between two species in which only one species benefits and neither is harmed.
commercial extinction
Depletion of a resource species to a point where it is no longer profitable to harvest the species.
community
The populations of all species that occupy a particular habitat and interact within that habitat.
compass
An instrument for showing direction by means of a magnetic needle swinging freely on a pivot and pointing to magnetic north.
compensation depth
The depth in the water column at which the production of carbohydrates and oxygen by photosynthesis exactly equals the consumption of carbohydrates and oxygen by respiration. The break-even point for autotrophs. Generally a function of light level.
compound
A substance composed of two or more elements in a fixed proportion.
condensation theory
Premise that stars and planets accumulate from contracting, accreting clouds of galactic gas, dust, and debris.
conduction
The transfer of heat through matter by the collision of one atom with another.
conservative constituent
An element that occurs in constant proportion in seawater. For example, chlorine, sodium, and magnesium.
constructive interference
The addition of wave energy as waves interact producing larger waves.
consumer
A heterotrophic organism.
continental crust
Solid, outer layers of earth, including the rocks of the continents
continental crust
The solid masses of the continents, composed primarily of granite.
continental drift
The theory that the continents move slowly across the surface of the earth.
continental margin
The submerged outer edge of a continent, made of granitic crust. Includes the continental shelf and continental slope. Compare ocean basin.
continental rise
Gently sloping base of the continental slope.
continental rise
The wedge of sediment forming the gentle transition from the outer (lower) edge of the continental slope to the abyssal plain. Usually associated with passive margins.
continental shelf
the shallow, gently sloping edge of a continental landmass where it meets the sea.
continental shelf
Gradually sloping submerged extension of a continent composed of granitic rock overlain by sediments. Has features similar to the edge of the nearby continent.
continental shelf break
Zone along which there is a marked increase of slope at the outer margin of a continental shelf.
continental slope
The steeply inclined edge of a continental plate below the continental shelf.
continental slope
The sloping transition between the granite of the continent and the basalt of the seabed. The true edge of a continent.
contour current
A bottom current made up of dense water that flows around (rather than over) seabed projections.
convection cell
Circulation in a fluid, or fluidlike material, caused by heating from below. Heating the base of a fluid lowers its density, causing it to rise. The rising fluid cools, becomes denser, and sinks, creating circulation.
convection cell
Movement within a fluid resulting from differential heating and cooling of the fluid. Convection produces mass transport or mixing of the fluid.
convection current
A single closed-flow circuit of rising warm material and falling cool material.
convergence zone
The line along which waters of different density converge. Convergence zones form the boundaries of tropical, sub-tropical, temperate, and polar regions.
convergent evolution
The evolution of similar characteristics in organisms of different ancestry; the body shape of a porpoise and a shark, for instance.
convergent plate boundary
A region where plates are pushing together and where a mountain range, island arc, and/or trench will eventually form. Often a site of much seismic and volcanic activity.
Cook, James
(1728-1779) Officer in the British Royal Navy who led the first European voyages of scientific discovery.
copepod
Small, shrimplike member of the zooplankton; in the class Crustacea.
coral
Any of over 6,000 species of small cnidarians, many of which are capable of generating hard calcareous (aragonite CaCO3) skeletons.
coral reef
A linear mass of calcium carbonate (aragonite and calcite) assembled from coral organisms, algae, mollusks, worms, and so on. Coral may contribute to less than half of the reef material.
corange lines
In a rotary tide, lines of equal tidal range about the amphidromic point.
core
The innermost layer of the Earth, composed primarily of iron, with nickel and heavy elements. The inner core is thought to be a solid 6,000°C (11,000°F) sphere, the outer core a 5,000°C (9,000°F) liquid mass. The average density of the outer core is about 11.8 g/cm3, and that of the inner core is about 16 g/cm3.
corer
Device that plunges a hollow tube into bottom sediments to extract a vertical sample.
Coriolis effect
The apparent deflection of a moving object from its initial course when its speed and direction are measured in reference to the surface of the rotating Earth. The object is deflected to the right of its anticipated course in the Northern hemisphere and to the left in the Southern Hemisphere. The deflection occurs for any horizontal movement of objects and has no effect at the equator.
Coriolis, Gaspard Gustave de
(1792-1843) The French scientist who in 1835 worked out the mathematics of the motion of bodies on a rotating surface. Refer to Coriolis effect.
cosmogenous sediment
Sediment of extraterrestrial origin.
counterclockwise
Rotation around a point in the direction opposite to that in which clock hands move. Also called anticlockwise.
countercurrent
A surface current flowing in the opposite direction from an adjacent surface current.
covalent bond
A chemical bond formed between two atoms by electron sharing.
crest
Highest part of a progressive wave above average water level.
crust
The outermost solid layer of Earth, composed mostly of granite and basalt; the top layer of the lithosphere. The crust has a density of 2.7-2.9 g/cm3 and accounts for 0.4% of Earth's mass.
Crustacea
The class of phylum Arthropoda to which lobsters, shrimp, barnacles, crabs, and copepods belong.
crustaceans
Invertebrates with jointed limbs and hard chalky shells, such as lobsters, crabs, and shrimp.
crustal plate
A segment of Earth's surface. Continental plates are about 25 miles thick and oceanic plates 3.1 miles thick.
cryptic coloration
Camouflage. May be active (under control of the animal) or passive (an unalterable color or shape).
current
A flow of water in the sea, generated by wind, tidal movements, or thermohaline circulation.
current
Mass flow of water. (The term is usually reserved for horizontal movement.)
cyclone
A weather system with a low-pressure area in the center around which winds blow counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. Not to be confused with a tornado, a much smaller weather phenomenon associated with sever thunderstorms. Se also extratropical cyclone; tropical cyclone.
Darwin, Charles
(1809-1882) English biologist. Co-discoverer (with Alfred Russell Wallace) of evolution by natural selection.
deadweight ton
(DWT) Capacity of a vessel in tons of cargo, fuel, stores, and so on; determined by the weight of the water displace.
declinational tide
See diurnal tide
deep scattering layer (DSL)
A relatively dense aggregation of fishes, squid, and other mesopelagic organisms capable of reflecting a sonar pulse that resembles a false bottom in the ocean. Its position varies with the time of day.
deep zone
The zone of the ocean below the pycnocline, in which there is little additional change of density with increasing depth. Contains about 80% of the world's water.
deep-water wave
A wave in water deeper than one-half its wavelength.
degree
An arbitrary measure of temperature. One degree Celsius (°C) equals 1.8 degrees Fahrenheit (°F).
delta
The deposit of sediments found at a river mouth, sometimes triangular in shape (hence the name after the Greek letter).
demersal fish
Fish living near and on the bottom.
density
The mass per unit volume of a substance, usually expressed in grams per cubic centimeter (g/cm3); the mass of a substance for a given volume.
density curve
A graph showing the relationship between a fluid's temperature or salinity and its density.
absolute dating
Determining the age of a geological sample by calculations of radioactive decay and/or its position in relation to other samples.
absorption
Conversion of sound or light energy into heat.
abyssal clay
lithogenous sediment on the deep-sea floor composed of at least 70% clay-sized particles by weight.
abyssal hill
Small sediment-covered inactive volcano or intrusion of molten rock less than 200 meters high, thought to be associated with sea-floor spreading. Abyssal hills punctuate the otherwise flat abyssal plain.
abyssal plain
Flat, cold, sediment-covered ocean floor between the continental rise and the mid-oceanic ridge at a depth of 3,700 to 5,300 meters. Abyssal plains are more extensive in the Atlantic and Indian Oceans than in the Pacific.
abyssal storm
Storm-like occurrences of rapid current movement affecting the deep ocean floor. They are believed to be caused by warm- and cold-core eddies of surface currents.
abyssal zone
The ocean between 13,120 and 19,680 feet deep.
abyssopelagic
Oceanic zone from 4000m to the deepest depth.
accessory pigment
One of the class of pigments (such as fucoxanthin, phycobilin, and xanthophyll) present in various photosynthetic plants and that assist in the absorption of light and the transfer of its energy to chlorophyll. Also called masking pigment.
accretion
An increase in the mass of a body by accumulation or a clumping of smaller particles.
acid
A substance that releases a hydrogen ion (H+) in solution.
acid rain
Rain containing acids and acid-forming compounds such as sulfur dioxide and oxides of nitrogen.
acoelomate
Without a secondary body cavity (coelom).
acoustic profiling
The use of seismic energy to measure sediment thickness and layering on the sea floor.
acoustic thermometry of ocean climate
ATOC; the measurement of ocean-wide changes in water properties such as temperature by transmitting and receiving low frequency sound signals.
acoustical tomography
A technique for studying ocean structure that depends on pulses of low frequency sounds to sense difference in water temperature, salinity, and movement beneath the surface.
action plan for the human environment
In 1972 this UN program established 12 worldwide environmental units and determined procedures for assessing and monitoring various sources of pollution.
active margin
Continental margin near an area of lithospheric plate convergence. Also called Pacific Type Margin.
active sonar
A device that generates underwater sound from special transducers and analyzes the returning echoes to gain information of geological, biological, or military importance.
active transport
The movement of molecules from a region of low concentration to a region of high concentration through a semipermeable membrane at the expense of energy.
adaptation
An inheritable structural or behavioral modification. A favorable adaptation gives a species an advantage in survival and reproduction. An unfavorable adaptation lessens a species ability to survive and reproduce.
adhesion
Attachment of water molecules to other substances of hydrogen bonds. Wetting.
adiabatic
Pertaining to a change in the temp of a mass resulting from compression or expansion; requires no addition of heat to or loss of heat from the substance.
adsorption
Attraction of ions to a solid surface.
advection
Horizontal or vertical transport of seawater, as by a current.
agar
Substance produced by red algae; the gelatin-like product of these algae.
Agnatha
The class of jawless fishes: hagfishes and lampreys.
ahermatypic
Describing coral species lacking symbiotic zooxanthellae and incapable of secreting calcium carbonate at a rate suitable for reef production.
air mass
A large mass of air with nearly uniform temperature, humidity, and density throughout.
Alaska gyre
A small Pacific Ocean subpolar surface current gyre that rotates counter-clockwise south of Alaska.
algae
Collective term for nonvascular plants possessing chlorophyll and capable of photosynthesis. Simple plants found as single cells or as seaweeds.
algin
A mucilaginous commercial product of multicellular marine algae. Widely used as a thickening and emulsifying agent.
Algulhas Current
A warm current that carries Indian Ocean water around the southern tip of Africa and into the Atlantic Ocean.
alkaline
Basic. See also base.
alluvial plain
A flat deposit of terrestrial sediment eroded by water from higher elevations.
alternation of generations
A reproductive cycle in which a plant alternates between sexual and asexual stages.
alveoli
A tiny thin-walled capillary rich sack in the lungs where the exchange of oxygen and carbon dioxide take place.
amnesic shellfish poisoning
Poisoning caused by demic acid secreted by a diatom. It has been known to kill birds and humans and obtains its name from the fact that the pervasive symptoms in humans is amnesia.
amphidromic point
A "no-tide" point in an ocean caused by basin resonances, friction, and other factors around which tide crests rotate. About a dozen amphidromic points exist in the world ocean. Also sometimes called a node.
anaerobic
Living or functioning in the absence of oxygen.
andesite
A volcanic rock intermediate in composition between basalt and granite; associated with subduction zones.
angiosperm
A flowering vascular plant that reproduces by means of a seed-bearing fruit. Examples are sea grasses and mangroves.
angle of incidence
In meteorology, the angle of the sun above the horizon.
animal
A multicellular organism unable to synthesize its own food and often capable of movement.
Animalia
The kingdom to which multicellular heterotrophs belong.
Annelida
The phylum of animals to which segmented worms belong.
anoxic
Deficient in oxygen.
Antarctic Bottom Water
The densest ocean water (1.0279 g/cm3), formed primarily in Antarctica's Weddell Sea during Southern Hemisphere winters.
Antarctic Circle
The line of latitude at 66°33'S marking the northern limit of the Antarctic region. The imaginary line around the Earth, parallel to the equator at 66°33'S, marking the southernmost limit of sunlight at the June solstice. The Antarctic Circle marks the northern limit of the area within which, for one day or more each year, the sun does not sea (around December 21) or rise (around June 21).
Antarctic Circumpolar Current
The current driven by powerful westerly winds north of Antarctica. The largest of all ocean currents, it continues permanently eastward without changing direction.
Antarctic Convergence
Convergence zone encircling Antarctica between about 50° and 60°S, marking the boundary between Antarctic Circumpolar Water and Subantarctic Surface Water.
Antarctic Ocean
An ocean in the Southern Hemisphere bounded to the north by the Atlantic Convergence and to the south by Antarctica.
antinode
Portion of a standing wave with maximum vertical motion.
aphelion
The point in the orbit of a satellite where it is farthest from the sun; opposite of perihelion.
aphotic zone
The part of the ocean where no surface light can penetrate.
apogean tide
A monthly tide of decreased range that occurs when the moon is farthest from earth (at apogee)
apogee
The point in the orbit of a satellite farthest from the main body; opposite of perigee.
aquaculture
The growing or farming of plants and animals in a water environment under controlled conditions. Compare mariculture.
Arctic Circle
The line of latitude at 66°33'N marking the southern limit of where the sun does not set in June or rise at December solstices.
Arctic Convergence
Convergence zone between Arctic Water and Subarctic Surface Water.
Arctic Ocean
An ice-covered ocean north of the continents of North America and Eurasia.
armored beach
A beach that is protected from wave and water erosion by coarse-size lag deposits.
Arthropoda
The phylum of animals that includes shrimp, lobsters, krill, barnacles, and insects. The phylum Arthropoda is the world's most successful.
artificial system of classification
A method of classifying an object based on attributes other than its reason for existence, its ancestry, or its origin. Compare natural system of classification.
ascidian
The sea squirts- a group of invertebrates that produce a larva with a primitive backbone.
aseimic ridge
see transverse ridge
Asteroidea
The class of the phylum Echinodermata to which sea stars belong.
asthenosphere
The hot, plastic layer of the upper mantle below the lithosphere, extending some 350 to 650 kilometers below the surface. Convection currents within the asthenosphere power plate tectonics.
astrolabe
An early navigation instrument that was the forerunner of the sextant.
atmospheric circulation cell
Large circuit of air driven by uneven solar heating and the Coriolis effect. Three circulation cells form in each hemisphere. See also Ferrel cell; Hadley cell; polar cell.
atmospheric pressure
Pressure, at any point on Earth, exerted by the atmosphere as a consequence of gravitational force exerted on the column of air lying directly above the point.
atoll
A ring-shaped island of coral reefs and coral debris enclosing, or almost enclosing, a central shallow lagoon from which no land protrudes. Atolls often form over sinking, inactive volcanoes.
atom
The smallest particle of an element that exhibits the characteristics of that element.
ATP
Adenosine triphosphate, the compound that acts as the immediate source of energy for all life on Earth. The energy stored in ATP is provided directly by photosynthesis or by respiration of glucose.
attenuation
Decrease in the energy of a wave or beam of particles occurring as the distance from the source increases; caused by absorption, scattering, and divergence from a point source.
authogenic sediment
Sediment formed directly by precipitation from seawater. Also called hydrogenous sediment.
autotroph
An organism that makes its own food by photosynthesis or chemosynthesis.
auxospore
A naked diatom cell without valves. Often a dormant stage in the life cycle following sexual reproduction.
Aves
The class of birds.
backshore
That part or zone of a beach profile that extends landward from the sloping foreshore to a point of either vegetation development or a change of physiography, e.g. a sea cliff or a dune field.
backshore
Sand on the shoreward side of the berm crest, sloping away from the ocean.
backwash
The water retreating down the shore after an incoming wave.
backwash
Water returning to the ocean from waves washing onto a beach.
bacteria
Single-celled prokaryotes, organisms lacking membrane-bound organelles.
Baguio
The local name given to tropical cyclones in the Philippines, especially those occurring from July to November.
Balearic Sea
One of the seas that comprise the western basin of the Mediterranean Sea which is sometimes called the Catalan Sea. It lies between The Iberian coast and the Balearic Islands (Ibiza, Mallorca, Menorca) in the northwestern Mediterranean.
baleen
The interleaved, hard, fibrous, hornlike filters within the mouth of baleen whales.
Bali Sea
A regional sea which is part of the Australasian Mediterranean Sea in the southwest Pacific Ocean. It is centered at around 116°E and 8.5°S and is bordered by Bali and Sumbawa to the south and Madura to the west.
Baltic Sea
A dilution basin type of Mediterranean sea that is connected to and experiences limited, intermittent water exchange with the North Sea.
bank
An undersea feature; and elevation of the sea floor, over which the depth of water is relatively shallow, but sufficient for safe surface navigation.
bar
Offshore ridge or mound of sand, gravel, or other loose material that is submerged, at least at high tide; located especially at the mouth of a river or estuary or lying a short distance from and parallel to the beach; A submerged or emerged mound of sand, gravel, or shell material built on the ocean floor in shallow water by waves and currents.
Barents Sea
One of the seas found on the Siberian shelf in the Arctic Mediterranean Sea. It is located between the White Sea to the west and the Kara Sea to the east and adjoins the Arctic Ocean proper to the north.
baroclinic
Descriptive of an atmosphere or ocean in which surfaces of pressure and density intersect at some level or levels. The state of the real atmosphere and ocean, as opposed to barotropic.
barotropic
Descriptive of a hypothetical atmosphere or ocean in which surfaces of pressure (isobaric surfaces) and density (isentropic surfaces) coincide at all levels, as compared to baroclinic. In a state of barotropic stratification, no potential energy is available for conversion to kinetic energy.
barrier island
A long, narrow, wave-built island lying parallel to the mainland and separated from it by a lagoon or bay. Compare sea island.
barrier layer
the layer between the thermocline and the halocline
barrier reef
One of three geomorphologically distinct types of coral reefs, the other two being fringing reefs and atolls. Barrier reefs are separated from land by a lagoon usually formed by coastal subsidence; A coral reef around islands or along continental coasts, with a deep lagoon between the reef and the coast.
barrier reef
A coral reef surrounding an island or lying parallel to the shore of a continent, separated from land by a deep lagoon. Coral debris islands may form along the reef.
barycenter
Center of mass and center rotation of the Earth-moon system, 1,700 kilometers inside Earth.
basalt
The relatively heavy crustal rock that forms the seabeds, composed mostly of oxygen, silicon, magnesium, and iron. Its density is about 2.9 g/cm3.
base
A substance that combines with a hydrogen ion (H+) in solution.
basin
An undersea feature; a depression, in the sea floor, more or less equidimensional in plan and of variable extent; large depression of the sea floor having about equal dimensions of length and width.
bathyal zone
The marine ecologic zone that lies deeper than the continental shelf but shallower than the deep ocean floor, i.e. those depths corresponding to the locations of the continental slope and rise.
bathyal zone
The ocean between about 200 and 4,000 meters deep.
bathybius
Thomas Henry Huxley's name for an artifact of marine specimen preservation he thought was a remnant of the "primeval living slime."
bathymetry
the measurement and charting of the spatial variation of the ocean depths.
bathymetry
The discovery and study of submerged contours.
bathypelagic zone
The ocean between 656 and 13,120 feet deep; One of five vertical ecological zones into which the deep sea is sometimes divided. This is the zone starting from 100 to 700 m deep (coinciding with the upper limit of the psychrosphere) at the 10°C isotherm.
bathyscaphe
Deep-diving submersible designed like a blimp, which uses gasoline for buoyancy and can reach the bottom of the deepest ocean trenches.
bathythermograph
A device developed by Athelstan Spilhaus in 1938 to measure temperature/depth profiles in the ocean. Replaced the oceanograph.
bay
A recess in the shore or an inlet of a sea between two capes or headlands, not as large as a gulf but larger than a cove.
bay mouth bar
An exposed sandbar attached to a headland adjacent to a bay and extending across the mouth of the bay.
Bay of Bengal
The northeastern arm of the Indian Ocean, located between India and Burma.
Bay of Nice
Located in the north western Mediterranean basin.
beach
The region of the shore where loose material, sand, mud, or pebble, are deposited between high- and low-water marks.
beach
A zone of unconsolidated (loose) particles extending from below water level to the edge of the coastal zone.
beach berm
The nearly horizontal portion of a beach formed by the deposition of sediment by receding waves. A beach may have more than one berm.
beach face
The sloping section of a beach profile below the beach berm which is normally exposed to the action of the wave swash.
beach scarp
Vertical wall of variable height marking the landward limit of the most recent high tides.
Beaufort scale
Scale of wind forces by range of velocity; scale of sea state created by winds of these velocities
Beaufort Sea
The marginal sea consisting of the waters off the northern coast of Alaska and Canada.
benthic
Descriptive of organisms that are attached to or resting on bottom sediments, as opposed to pelagic.
benthic zone
The seabed.
benthic zone
The zone of the ocean bottom. See also pelagic zone.
benthos
Organisms living on or in the ocean bottom.
Bering Sea
A marginal sea located on the northern rim of the Pacific Ocean centered at approximately 58°N and 160°W. It is surrounded by Alaska to the east, Siberia to the west, and the Aleutian Island arc to the south.
berm
A horizontal ridge of sand or shingle running parallel to the shore, at the limit of wave action.
berm
A nearly horizontal accumulation of sediment parallel to shore. Marks the normal limit of sand deposition by wave action.
berm crest
The seaward limit of a beach berm.
berm crest
The top of the berm, the highest point on most beaches. Corresponds to the shoreward limit of wave action during most high tides.
beta refraction
An effect that results from the latitudinal variation of Rossby wave phase speed which is, in turn, due to the beta effect. If a line of Rossby waves were started along a straight eastern ocean boundary, then those at low latitudes would arrive at the western boundary before those at high latitudes.
bias
The amount by which the average of a set of values departs from a reference value.
big bang
The hypothetical event that started the expansion of the universe from a geometric point. The beginning of time.
bilateral symmetry
Body structure having left and right sides that are approximate mirror images of each other. Examples are crabs and humans. Compare radial symmetry.
biodegradable
Able to be broken by natural processes into simpler compounds.
biodiversity
The variety of different species within a habitat.
biogenic
One of three major components of deep sea sediments, the other two being authigenic and detrital. Biogenic sediment consists mainly of calcite and opal produced as the hard parts of organisms and eventually precipitated.
biogenous sediment
Sediment of biological origin. Organisms can deposit calcareous (calcium-containing) or siliceous (silicon-containing) residue.
biogeochemical sediment
Natural processes that recycle nutrients in various chemical forms from the nonliving environment to the living organisms and then back to the nonliving environment.
biological amplification
Increase in concentration of certain fat-soluble chemicals such as DDT or heavy metal compounds, in successively higher trophic levels within a food web.
biological factor
A biologically generated aspect of the environment, such as predation or metabolic waste products, that affects living organisms. Biological factors usually operate in association with purely physical factors such as light and temperature.
biological pump
Photosynthetic transfer of carbon as CO2 from the atmosphere to the ocean in the form of organic molecules; carbon is transferred to intermediate and deep-ocean water when organic material sinks and decays.
biological resource
A living animal or plant collected for human use. Also called a living resource.
bioluminescence
The generation of light by living organisms using the enzyme luciferase.
bioluminescence
Biologically produced light.
biomass
The mass of living material in a given area or volume of habitat.
biosynthesis
The initial formation of life on Earth.
bioturbation
The stirring of sediment by animal life.
bioturbation
Reworking of sediments by organisms that burrow into them and ingest them.
Bivalvia
The class of phylum Mollusca that includes clams, oysters, and mussels.
Bjerknes, Vilhelm
(1862-1951) Pioneering Norwegian physicist and discoverer of the nature and formation of extratropical cyclones, which cause most mid-latitude weather.
Black Sea
A Mediterranean sea, centered at approximately 35°E and 44°N, that is the world's largest inland water basin.
Blade
Algal equivalent of a vascular plant's leaf. Also called a frond.
bloom
The sudden increase in phytoplankton number, usually associated with season changes.
bloom
High concentration of phytoplankton in an area, caused by increased reproduction; often produces discoloration of water. See red tide.
Bohol Sea
A small sea centered in the Philippines at about 124°E and 9°S.
bond
An energy relationship that holds two atoms together as a result of changes in their electron distribution.
borderland
undersea feature; a region adjacent to a continent, normally occupied by or bordering a shelf and sometimes emerging as islands.
Bowen ration
The ratio of the amount of sensible to that of latent heat lost by a surface to the atmosphere by the processes of conduction and turbulence.
brackish
Describing water intermediate in salinity between seawater and freshwater.
Bransfield Strait
A strait located between the northern tip of the Antarctica Peninsula and the South Shetland Islands. 120 km wide and extends 460 km from Clarence Island to Low Island.
brash ice
A type of sea ice; accumulations of floating ice made up of fragments not more than 2 meters across; the wreckage of other forms of ice.
Brazil Basin
An ocean basin located off the eastern coast of Brazil in the west-central Atlantic Ocean.
breaker
Sea surface water wave that has become too steep to be stable and collapses.
breaker zone
The portion of the nearshore zone where waves arriving from offshore become unstable and break
breakwater
Structure protecting a shore area, harbor, anchorage, or basin from waves; a type of jetty.
breakwater
An artificial structure of durable material that interrupts the progress of waves to shore. Harbors are often shielded by breakwater.
bucket temperature
The surface temperature of the ocean as measured by a bucket thermometer.
bucket thermometer
A thermometer with an insulated container around the bulb.
buffer
A group of substances that tends to resist change in the pH of a solution by combining with free ions.
buffer factor
Defined as the fractional changed in atmospheric CO2 divided by the fractional change in oceanic DIC after equilibrium has been reached.
buffer sublayer
That part of a boundary layer where the viscous stress and the Reynolds stress have the same order of magnitude and the linear velocity profile turns smoothly into the logarithmic profile.
bulkhead
Structure separating land and water areas; primarily designed to resist earth sliding and slumping or to reduce wave erosion at the base of a cliff.
buoy
Floating object to float due to the support of the fluid the body is in or on.
buoyancy
The ability of an object to float in a fluid by displacement of a volume of fluid equal to it in mass.
by-catch
See incidental catch.
bykill
Animals unintentionally killed when desirable organisms are collected.
caballing
Mixing of two water masses of identical densities but different temperatures and salinities, such that the resulting mixture is denser than its components.
cabbeling
A phenomenon that occurs when two water masses with identical densities but different temperatures and salinities mix to form a third water mass with a greater density than either of its constituents.
calcareous
Of or containing calcium carbonate or another, usually insoluble, calcium salt.
calcareous ooze
Partially composed organic matter mixed with a quantity of calcareous material on the bottom of some bodies of water; a fine-grained, deep-sea deposit of pelagic origin containing more than 30% calcium carbonate derived from the skeletal material of various plankton. It is the most extensive deposit on the ocean floor but restricted to depths less than about 3500 m due to the carbon compensation depth.
calcareous ooze
Ooze composed mostly of the hard remains of organisms containing calcium carbonate.
calcium carbonate compensation depth
The depth at which the rate of accumulation of calcareous sediments equals the rate of dissolution of those sediments. Below this depth, sediment contains little or no calcium carbonate.
caldera
undersea feature; a collapsed or partially-collapsed seamount, commonly of annular shape.
calorie
The amount of heat needed to raise the temperatures of 1 gram (0.035 ounce) of pure water by 1°C (1.8°F).
calving
Breaking away of a mass of ice from its parent glacier, iceberg, or sea ice formation.
Camotes Sea
A small sea within the Visayan Islands that comprise the middle portion of the Philippines.
Canary Basin
An ocean basin located to the west of the Canary Islands in the eastern North Atlantic Ocean.
canyon
Undersea feature; a relatively narrow, deep depression with steep sides, the bottom of which generally deepends continuously, developed characteristically on some continental slopes.
Cape Basin
An ocean basin located to the west of South Africa at about 35°S in the South Atlantic Ocean.
Cape Verde Basin
An ocean basin located at about 15°N off the west coast of Africa in the North Atlantic Ocean.
capillary wave
A wave on a fluid interface for which the restoring force is surface tension.
capillary wave
A tiny wave with a wavelength of less than 1.73 centimeters (0.68 inch), whose restoring force is surface tension; the first type of wave to form when the wind blows.
carbon cycle
The cycling of carbon in the form of carbon dioxide, carbonates, organic compounds, etc. between various reservoirs, e.g. the atmosphere, the oceans, land and marine biota and, on geological time scales, sediments, and rocks.
carbon dioxide
The most important of the greenhouse gases with an atmospheric concentration of 353 ppm.
carbon-14 dating
A radioisotope dating method wherein a radioactive isotope of carbon, also called radiocarbon, is used to date materials containing carbon.
carbonate compensation depth
(CCD) Also known as the calcite compensation depth, is the depth at which the amount of calcium carbonate preserved falls below 20% of the total sediment. This is also commonly defined as the depth at which the amount of calcium carbonate produced by organisms skeletal material in the overlying water column is equal to the rate at which it is dissolved in the water. No calcium carbonate will be deposited below this depth.
Cariaco Basin
A 1400 m deep depression within the continental shelf of Venezuela.
Caribbean Sea
The largest marginal sea of the Atlantic Ocean, with a surface area twice that of the Mediterranean Sea.
Carnivora
The order of mammals that includes seals, sea lions, walruses, and sea otters.
carrageenan
Substance produced by certain algae that acts as a thickening agent.
carrying capacity
The size at which a particular population in a particular environment will stabilize when its supply of resources--including nutrients, energy and living space -- remains constant.
cartilage
A tough, elastic tissue that stiffens or supports.
cartographer
A person who makes maps and charts.
Catalan Sea
See Balearic Sea
catastrophism
The theory that the Earth's surface features are formed by catastrophic forces such as the biblical flood. Catastrophists believe in a young Earth and a literal interpretation of the biblical account of Creation.
cat's-paw
Patch of ripples on the water's surface, related to a discrete gust of wind.
Celebes Sea
Alternate name for the Sulawesi Sea.
celestial navigation
The technique of finding one's position on Earth by reference to the apparent position of stars, planets, the moon, and the sun.
cell
The basic organizational unit of life on this planet.
Celtic Sea
A shallow embayment of the eastern North Atlantic bounded by Southern Ireland. Separated from the Irish Sea by a line drawn from Ramsey Island to Carnsore Point and from the English Channel by a line drawn from Ushant to Lands End.
Cenderawasih Bay
A bay on the northern coast of Irian Jaya centered at approximately 135°E and 2.5°S at the southwestern edge of the Pacific Ocean.
centers of action
Large semi permanent belts of high or low sea level pressure distributed around the Earth that largely control the general circulation of the atmosphere and the concomitant long-term weather patterns.
central water
A term used to identify thermocline water masses in all three oceans. The water arrives at a thermocline via a process known as subduction.
centrifugal force
Outward-directed force acting on a body moving along a curved path or rotating about an axis; an inertial force.
cephalopod
An advanced group of mollusks that includes the squids, octopuses, and cuttlefishes.
Cephalopoda
The class of the phylum Mollusca that includes squid, octopuses, and nautiluses.
cetacea
The order of mammals that includes porpoises, dolphins and whales.
cetaceans
The whales and dolphins.
CFCs
A class of halogenated hydrocarbons thought to be depleting Earth's atmospheric ozone. CFCs are used as cleaning agents, refrigerants, fire extinguishing fluids, spray can propellants, and insulating foams.
chaetognaths
Free-swimming, carnivorous, pelagic, wormlike, planktonic animals; arrowworms.
Challenger Expedition
The first wholly scientific oceanographic expedition, 1872-76. Named for the steam corvette used in the voyage.
channel
A body of water that connects two larger bodies of water. A channel is also part of a river or harbor that is deep enough to let ships sail through.
chart
A map that depicts mostly water and the adjoining land areas.
chemical bond
An energy relationship that holds two atoms together as a result of changes in their electron distribution.
chemical equilibrium
In seawater, the condition in which the proportion and amounts of dissolved salts per unit volume of ocean are nearly consistent.
chemosynthesis
The synthesis of organic compounds from inorganic compounds using energy stored in inorganic substances such as sulfur, ammonia, and hydrogen. Energy is released when these substances are oxidized by certain organisms.
chitin
A complex nitrogen-rich carbohydrate from which parts of arthropod exoskeletons are constructed.
chiton
A polyplasophoran mollusk.
chlorinated hydrocarbons
The most abundant and dangerous class of halogenated hydrocarbons, synthetic organic chemicals hazardous to the marine environment.
chlorine titration
The method developed by Knudsen in 1902 to determine the chlorinity and therefore salinity of a sea water sample.
chlorinity
A measure of the amount of chlorine or other halides in water (especially seawater).
chlorinity
A measure of the content of chloride, bromine, and iodide ions in seawater. We may derive salinity from chlorinity by multiplying by 1.80655.
chlorofluorocarbons
A class of halogenated hydrocarbons thought to be depleting Earth's atmospheric ozone. CFCs are used as cleaning agents, refrigerants, fire extinguishing fluids, spray can propellants, and insulating foams.
chlorophyll
A pigment responsible for trapping sunlight and transferring its energy to electrons, thus initiating photosynthesis.
Chlorophyta
Green algae.
Chondrichthyes
The class of fishes with cartilagenous skeletons: the sharks, skates, rays, and chimaeras.
Chordata
The phylum of animals to which tunicates, Amphioxus, fishes, amphibians, reptiles, birds, and mammals belong.
chromatophore
A pigmented skin cell that expands or contracts to affect color change.
chronometer
A watch or clock able to maintain its accuracy on long sea voyages.
chronometer
A very consistent clock. It doesn't need to tell accurate time, but its rate of gain or loss must be constant and known exactly so that accurate time may be calculated.
ciguatera
Toxin found in fish of tropical regions; produced by dinoflagellates.
cilia
Microscopic, hairlike projections of living cells that beat in coordinated fashion and produce movement.
clamshell sampler
Sampling device used to take shallow samples of the ocean bottom.
classification
A way of grouping objects according to some stated criteria.
clay
Sediment particle smaller than 0.004mm in diameter; the smallest sediment size category.
climate
The long-term average of weather in an area.
climax community
A stable, long-established community of self-perpetuating organisms that tends not to change with time.
clockwise
Rotation around a point in the direction that clock hands move.
clumped distribution
Distribution of organisms within a community in small, patchy aggregations, or clumps; the most common distribution pattern.
Cnidaria
The phylum of animals to which corals, jellyfish, and sea anemones belong.
cnidoblast
Type of cell found in members of the phylum Cnidaria that contains a stinging capsule. The threads that evert from the capsules assist in capturing prey and repelling aggressors.
coast
The zone extending from the ocean inland as far as the environment is immediately affected by marine processes.
coastal cell
The natural sector of a coastline in which sand input and sand outflow are balanced.
coastal upwelling
Upwelling adjacent to a coast, usually induced by wind.
coccolithophore
A very small planktonic alga carrying discs of calcium carbonate, which contributes to biogenous sediments.
cohesion
Attachment of water molecules to each other by hydrogen bonds.
cold seep
Cold seawater, rich in methane, hydrogen sulfide, and hydrocarbons issuing from the seafloor.
colligative properties
Those characteristics of a solution that differ from those of pure water because of material held in solution.
Columbus, Christopher
1451-1506. Italian explorer in the service of Spain who discovered islands in the Caribbean in 1492. Although traditionally credited as the discoverer of America, he never actually sighted the North American continent.
commensalism
A symbiotic interaction between two species in which only one species benefits and neither is harmed.
commercial extinction
Depletion of a resource species to a point where it is no longer profitable to harvest the species.
community
The populations of all species that occupy a particular habitat and interact within that habitat.
compass
An instrument for showing direction by means of a magnetic needle swinging freely on a pivot and pointing to magnetic north.
compensation depth
The depth in the water column at which the production of carbohydrates and oxygen by photosynthesis exactly equals the consumption of carbohydrates and oxygen by respiration. The break-even point for autotrophs. Generally a function of light level.
compound
A substance composed of two or more elements in a fixed proportion.
condensation theory
Premise that stars and planets accumulate from contracting, accreting clouds of galactic gas, dust, and debris.
conduction
The transfer of heat through matter by the collision of one atom with another.
conservative constituent
An element that occurs in constant proportion in seawater. For example, chlorine, sodium, and magnesium.
constructive interference
The addition of wave energy as waves interact producing larger waves.
consumer
A heterotrophic organism.
continental crust
Solid, outer layers of earth, including the rocks of the continents
continental crust
The solid masses of the continents, composed primarily of granite.
continental drift
The theory that the continents move slowly across the surface of the earth.
continental margin
The submerged outer edge of a continent, made of granitic crust. Includes the continental shelf and continental slope. Compare ocean basin.
continental rise
Gently sloping base of the continental slope.
continental rise
The wedge of sediment forming the gentle transition from the outer (lower) edge of the continental slope to the abyssal plain. Usually associated with passive margins.
continental shelf
the shallow, gently sloping edge of a continental landmass where it meets the sea.
continental shelf
Gradually sloping submerged extension of a continent composed of granitic rock overlain by sediments. Has features similar to the edge of the nearby continent.
continental shelf break
Zone along which there is a marked increase of slope at the outer margin of a continental shelf.
continental slope
The steeply inclined edge of a continental plate below the continental shelf.
continental slope
The sloping transition between the granite of the continent and the basalt of the seabed. The true edge of a continent.
contour current
A bottom current made up of dense water that flows around (rather than over) seabed projections.
convection cell
Circulation in a fluid, or fluidlike material, caused by heating from below. Heating the base of a fluid lowers its density, causing it to rise. The rising fluid cools, becomes denser, and sinks, creating circulation.
convection cell
Movement within a fluid resulting from differential heating and cooling of the fluid. Convection produces mass transport or mixing of the fluid.
convection current
A single closed-flow circuit of rising warm material and falling cool material.
convergence zone
The line along which waters of different density converge. Convergence zones form the boundaries of tropical, sub-tropical, temperate, and polar regions.
convergent evolution
The evolution of similar characteristics in organisms of different ancestry; the body shape of a porpoise and a shark, for instance.
convergent plate boundary
A region where plates are pushing together and where a mountain range, island arc, and/or trench will eventually form. Often a site of much seismic and volcanic activity.
Cook, James
(1728-1779) Officer in the British Royal Navy who led the first European voyages of scientific discovery.
copepod
Small, shrimplike member of the zooplankton; in the class Crustacea.
coral
Any of over 6,000 species of small cnidarians, many of which are capable of generating hard calcareous (aragonite CaCO3) skeletons.
coral reef
A linear mass of calcium carbonate (aragonite and calcite) assembled from coral organisms, algae, mollusks, worms, and so on. Coral may contribute to less than half of the reef material.
corange lines
In a rotary tide, lines of equal tidal range about the amphidromic point.
core
The innermost layer of the Earth, composed primarily of iron, with nickel and heavy elements. The inner core is thought to be a solid 6,000°C (11,000°F) sphere, the outer core a 5,000°C (9,000°F) liquid mass. The average density of the outer core is about 11.8 g/cm3, and that of the inner core is about 16 g/cm3.
corer
Device that plunges a hollow tube into bottom sediments to extract a vertical sample.
Coriolis effect
The apparent deflection of a moving object from its initial course when its speed and direction are measured in reference to the surface of the rotating Earth. The object is deflected to the right of its anticipated course in the Northern hemisphere and to the left in the Southern Hemisphere. The deflection occurs for any horizontal movement of objects and has no effect at the equator.
Coriolis, Gaspard Gustave de
(1792-1843) The French scientist who in 1835 worked out the mathematics of the motion of bodies on a rotating surface. Refer to Coriolis effect.
cosmogenous sediment
Sediment of extraterrestrial origin.
counterclockwise
Rotation around a point in the direction opposite to that in which clock hands move. Also called anticlockwise.
countercurrent
A surface current flowing in the opposite direction from an adjacent surface current.
covalent bond
A chemical bond formed between two atoms by electron sharing.
crest
Highest part of a progressive wave above average water level.
crust
The outermost solid layer of Earth, composed mostly of granite and basalt; the top layer of the lithosphere. The crust has a density of 2.7-2.9 g/cm3 and accounts for 0.4% of Earth's mass.
Crustacea
The class of phylum Arthropoda to which lobsters, shrimp, barnacles, crabs, and copepods belong.
crustaceans
Invertebrates with jointed limbs and hard chalky shells, such as lobsters, crabs, and shrimp.
crustal plate
A segment of Earth's surface. Continental plates are about 25 miles thick and oceanic plates 3.1 miles thick.
cryptic coloration
Camouflage. May be active (under control of the animal) or passive (an unalterable color or shape).
current
A flow of water in the sea, generated by wind, tidal movements, or thermohaline circulation.
current
Mass flow of water. (The term is usually reserved for horizontal movement.)
cyclone
A weather system with a low-pressure area in the center around which winds blow counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. Not to be confused with a tornado, a much smaller weather phenomenon associated with sever thunderstorms. Se also extratropical cyclone; tropical cyclone.
Darwin, Charles
(1809-1882) English biologist. Co-discoverer (with Alfred Russell Wallace) of evolution by natural selection.
deadweight ton
(DWT) Capacity of a vessel in tons of cargo, fuel, stores, and so on; determined by the weight of the water displace.
declinational tide
See diurnal tide
deep scattering layer (DSL)
A relatively dense aggregation of fishes, squid, and other mesopelagic organisms capable of reflecting a sonar pulse that resembles a false bottom in the ocean. Its position varies with the time of day.
deep zone
The zone of the ocean below the pycnocline, in which there is little additional change of density with increasing depth. Contains about 80% of the world's water.
deep-water wave
A wave in water deeper than one-half its wavelength.
degree
An arbitrary measure of temperature. One degree Celsius (°C) equals 1.8 degrees Fahrenheit (°F).
delta
The deposit of sediments found at a river mouth, sometimes triangular in shape (hence the name after the Greek letter).
demersal fish
Fish living near and on the bottom.
density
The mass per unit volume of a substance, usually expressed in grams per cubic centimeter (g/cm3); the mass of a substance for a given volume.
density curve
A graph showing the relationship between a fluid's temperature or salinity and its density.
density stratification
The formation of layers in a material, with each deeper layer being denser (weighing more per unit of volume) than the layer above.
dependency
A feeding relationship in which an organism is limited to feeding on one species or, in extreme cases, on one size phase of one species.
deposition
Accumulation, usually of sediments.
depositional coast
A coast in which processes that deposit sediment exceed erosive processes.
desalination
The process of removing salt from seawater or brackish water.
desiccation
Drying.
destructive interference
The subtraction of wave energy as waves interact, producing smaller waves.
detritus
Any loose material, especially decomposed, broken, and dead organic materials.
diatom
Earth's most abundant, successful, and efficient single-celled phytoplankton. Diatoms possess two interlocking valves made primarily of silica. The valves contribute to biogenous sediments.
diatomaceous ooze
Sediment made up of more than 30% skeletal remains of diatoms.
diffusion
The movement--driven by heat-- of molecules from a region of high concentration to a region of low concentration.
dinoflagellate
One of a class of microscopic single-celled flagellates, not all of which are autotrophic. The outer covering is often of stiff cellulose. Planktonic dinoflagellates are responsible for "red tides".
dispersion
Separation of wind waves by wavelength (and therefore wave speed) as they move away from the fetch (the place of their formation). Dispersion occurs because waves with long wavelengths move more rapidly than waves with short wavelengths.
disphotic zone
The lower part of the photic zone, where there is insufficient light for photosynthesis.
dissolution
The dissolving by water of minerals in the rocks.
disthermal zone
The zone of stable temperature below the thermocline.
disturbing force
The energy that causes a wave to form.
diurnal
Applies to a location that normally experiences one high water and one low water during a tidal day of 24 hours.
diurnal inequality
Difference in height between two high waters or two low waters of each tidal day; the difference in speed between the two flood currents or two ebb currents of each tidal day.
diurnal tide
A tidal cycle of one high tide and one low tide per day.
divergent evolution
Evolutionary radiation of different species from a common ancestor.
divergent plate boundary
A region where plates are moving apart and where new ocean or rift valley will eventually form. A spreading center forms the junction.
dobson unit
Ozone unit, defined as 0.01 mm thickness of ozone at Standard Temperature and Pressure. If all the ozone over a certain area is compressed to 1 atm pressure at 0°C, it forms a slab of a thickness corresponding to a number of Dobson units.
doldrums
The zone of rising air near the equator known for sultry air and variable breezes. See also intertropical convergence zone (ITCZ).
downwelling
Circulation pattern in which surface water moves vertically downward.
drag
The resistance to movement of an organism induced by the fluid through which it swims.
dredge
Cyllindric or boxlike sampling device made of metal, net, or both, that is dragged across the bottom to obtain biological or geological samples.
drift bottle
Bottle released into the sea for use in studying currents; contains a card identifying date and place of release and requesting the finder to return it with date and place of recovery.
drift net
Fine, vertically suspended net that may be 7 meters (25 feet) high and 80 kilometers (50 miles) long.
drift sector
See coastal circulation cell.
drumlin
A streamlined hill formed by a glacier.
DSL
Deep Scattering Layer: A relatively dense aggregation of fishes, squid, and other mesopelagic organisms capable of reflecting a sonar pulse that resembles a false bottom in the ocean. Its position varies with the time of day.
dugong
See sea cow.
dune
An accumulation of wind-blown sand often found above the high-tide mark on sand shores. Also, a great book by Frank Herbert!
dynamic equilibrium
State in which the sums of all changes are balanced and there is no net charge.
dynamic theory of tides
Model of tides that takes into account the effects of finite ocean depth, basin resonances, and the interference of continents on tide waves.
earth sphere depth
Uniform depth of earth below the present mean sea level, if the solid earth surface were smoothed off evenly (2440 m).
earthquake
A sudden motion of Earth's crust resulting from waves in Earth caused by faulting of the rocks or by volcanic activity.
eastern boundary current
Weak, cold, diffuse, slow-moving current at the eastern boundary of an ocean (off the west coast of a continent). Examples include the Canary Current and the Humboldt Current.
ebb current
Water rushing out of an enclosed harbor or bay because of the fall in sea level as a tide trough approaches.
ebb tide
tide period between high and low water; falling tide; the period of the tide between high water and the next low water.
Echinodermata
The phylum of exclusively marine animals to which sea stars, brittle stars, sea urchins, and sea cucumbers belong.
Echinoidea
The class of the phylum Echinodermata to which sea urchins and sand dollars belong.
echo sounder
A device that reflects sound off the ocean bottom to sense water depth. Its accuracy is affected by the variability of the speed of sound through water.
echolocation
The use of sound by whales and dolphins to sense objects.
echolocation
The use of reflected sound to detect environmental objects. Cetaceans use echolocation to detect prey and avoid obstacles.
ecology
Study of the interactions of organisms with one another and with their environment.
ectoderm
The outermost layer of cells in a developing embryo.
ectotherm
An organism incapable of generating and maintaining steady internal temperature from metabolic heat and therefore whose internal body temperature is approximately the same as that of the surrounding environment. A cold-blooded organism.
eddy
A circular movement in water produced by flows around obstructions or by interacting currents.
eddy
A circular movement of water usually formed where currents pass obstructions, or between two adjacent currents flowing in opposite directions, or along the edge of a permanent current.
EEZ
exclusive economic zone: The offshore zone claimed by signatories to the 1982 United Nations Draft Convention of the Law of the Sea. The EEZ extends 200 nautical miles (370 kilometers) from a contiguous shoreline. See also United States Exclusive Economic Zone.
Ekman spiral
A theoretical model of the effect on water of wind blowing over the ocean. Because of the Coriolis effect, the surface layer is expected to drift at an angle of 45° to the right of the wind in the Northern hemisphere and 45° to the left in the Southern Hemisphere. Water at successively lower layers drifts progressively to the right (N) or left (S), though not as swiftly as the surface flow.
Ekman transport
Net water transport, the sum of layer movement due to the Ekman spiral. Theoretical Ekman transport in the Northern Hemisphere is 90° to the right of wind direction.
El Niño
The periodic warming of the surface waters in the east Pacific that stops upwelling of nutrients.
El Niño
A southward-flowing nutrient-poor current of warm water off the coast of western South America, caused by a breakdown of trade-wind circulation.
electrodialysis
Separation process in which electrodes of opposite charge are placed on each side of a semipermeable membrane to accelerate the diffusion of ions across the membrane.
electromagnetic radiation
Waves of energy formed by simultaneous electrical and magnetic oscillations, the electromagnetic spectrum is the continuum of all electromagnetic radiation from low-energy radio waves to high-energy gamma rays, including visible light.
electron
A tiny negatively charged particle in an atom responsible for chemical bonding.
element
A substance composed of identical atoms that cannot be broken into simpler substances by chemical means.
endoderm
The innermost layer of cells in a developing embryo.
endotherm
An organism capable of generating and regulating metabolic heat to maintain a steady internal temperature. Birds and mammals are the only animals capable of true endothermy. A warm-blooded organism.
energy
The capacity to do work.
ENSO
Acronym for the coupled phenomena of El Niño and the Southern Oscillation. El Niño is a southward-flowing nutrient-poor current of warm water off the coast of western South America, caused by a breakdown of trade-wind circulation. Southern Oscillation is a reversal of airflow between normally low atmospheric pressure over the western Pacific and normally high pressure over the Eastern Pacific, and is the cause of El Niño.
entrainment
Mixing of salt water into fresh water overlying salt water, as in an estuary.
entropy
A measure of the disorder in a system.
environmental resistance
All of the limiting factors that act together to regulate the maximum allowable size, or carrying capacity, of a population.
epicenter
The point on Earth's surface directly above the focus of an earthquake.
epifauna
Animals living attached to the sea bottom or moving freely over it.
epipelagic zone
The lighted, or photic, zone in the ocean.
episodic wave
Abnormally high wave unrelated to a local storm conditions.
equator
0° latitude, an imaginary line equidistant from the geographical poles. See also geographical equator and meteorological equator.
equatorial upwelling
Upwelling in which water moving westward on either side of the geographical equator tends to be deflected slightly poleward and replaced by deep water often rich in nutrients. See also upwelling.
equilibrium theory of tides
Idealized model of tides that considers earth to be covered by an ocean of great and uniform depth capable of instantaneous response to the gravitational and inertial forces of the sun and the moon.
equinoxes
Days of the year when the sun stands directly above the equator, so that day and night are of equal length around the world. The vernal equinox occurs about March 21, and the autumnal equinox occurs September 22-23.
Eratosthenes of Cyrene
(276-192 BC) Greek scholar and librarian at Alexandria who first calculated the circumference of the Earth about 230 BC.
erosion
A process of being gradually worn away.
erosional coast
A coast in which erosive processes exceed depositional ones.
escarpment
Nearly continuous line of cliffs or steep slopes caused by erosion or faulting.
estuary
A semi-enclosed area of water where fresh and saltwater mix.
estuary
A body of water partially surrounded by land where fresh water from a river mixes with ocean water, creating an area of remarkable biological productivity.
euphausiid
Planktonic, shrimplike crustacean, see also krill.
euphotic zone
The upper layers where light is sufficient for photosynthesis.
euphotic zone
The upper layer of the photic zone in which net photosynthetic gain occurs. Part of the photic zone, which is the thin film of lighted water at the top of the world ocean. The photic zone rarely extends deeper than 200 meters (660 feet).
euryhaline
Describing an organism able to tolerate a wide range of salinity.
eurythermal
Describing an organism able to tolerate a wide range of temperature.
eurythermal zone
The upper layer of water, where temperature changes with the seasons.
eustatic change
Global change in sea level that affects all the world's coastlines.
eustatic change
A worldwide change in sea level, as distinct from local changes.
eutrophication
A set of chemical, physical, and biological changes brought about when excessive nutrients are released into water.
evaporite
Deposit formed by the evaporation of ocean water.
evapotranspiration
The combined effect of evaporation and transpiration.
evolution
Change. The maintenance of life under constantly changing conditions by continuous adaptation of successive generations of a species to its environment.
excess volatiles
A compound found in the ocean and atmosphere in quantities greater than can be accounted for by the weathering of surface rock. Such compounds probably entered the atmosphere and ocean from deep crustal and upper mantle sources through volcanism.
Exclusive economic zone (EEZ)
The offshore zone claimed by signatories to the 1982 United Nations Draft Convention of the Law of the Sea. The EEZ extends 200 nautical miles (370 kilometers) from a contiguous shoreline. See also United States Exclusive Economic Zone.
exoskeleton
A strong, lightweight, form-fitted external covering and support common to animals of the phylum Arthropoda. The exoskeleton is made partly of chitin and may be strengthened by calcium carbonate.
experiments
tests that simplify observation in nature or in the laboratory by manipulating or controlling the conditions under which observations are made.
extratropical cyclone
A low-pressure mid-latitude weather system characterized by converging winds and ascending air rotating counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. An extratropical cyclone forms at the front between the polar and Ferrel cells.
extremophile
Microorganism that thrives under extreme conditions of temperature, lack of oxygen, or high acid or salt levels; these conditions kill most other organisms.
falling tide
tide period between high and low water. Also known as ebb tide.
fast ice
Sea ice that is anchored to shore or the sea floor in shallow water.
fathom
A unit of length equal to 1.8m (6ft); used to measure water depth.
fault
A fracture in a rock mass along which movement has occurred.
Ferrel cell
The middle atmospheric circulation cell in each hemisphere. Air in these cells rises at 60° latitude and falls at 30° latitude. See also westerlies.
Ferrel, William
(1817-1891) The American scientist who discovered the mid-latitude circulation cells of each hemisphere.
fetch
The distance over water in which waves are generated by a wind having a rather constant direction and speed.
fetch
The uninterrupted distance over which the wind blows without a significant change in direction, a factor in wind wave development.
filament
Chain of living cells.
Fissipedia
The carnivoran suborder that includes sea otters.
fjord
A deep, narrow estuary in a valley originally cut by a glacier.
flagellum
A whiplike structure used by some small organisms and gametes to move through the environment. (Plural, flagella.)
float method
A method of current study that depends on the movement of a drift bottle or other free-floating object.
floe
Discrete patch of sea ice moved by the currents or wind.
flood current
Water rushing into an enclosed harbor or bay because of the rise in sea level as a tide crest approaches.
flood tide
The period of tide between low water and high water. Also known as a rising tide.
flood tide
Rising tide; the period of the tide between low water and the next high water.
flow method
A method of current study that measures the current as it floats past a fixed object.
flushing time
Length of time required for an estuary to exchange its water depth with the open ocean.
focus
The location of an earthquake within earth. Focus is specified by identifying latitude, longitude, and depth of the earthquake. See also epicenter.
food
General term for organic molecules capable of providing energy to heterotrophs when combined with oxygen during biochemical respiration.
food web
A group of organisms associated by a complex set of feeding relationships in which the flow of food energy can be followed from primary producers through consumers.
foraminiferan
One of a group of planktonic amoeba-like animals with a calcareous shell, which contributes to biogenous sediments.
forced wave
A progressive wave under the continuing influence of the forces that formed it. Compare to free wave.
Forchhammer's principle
The proportions of major conservative elements in seawater remain nearly constant, though total salinity may change with location Also called the principle of constant proportions.
foreshore
Portion of the shore that includes the low-tide terrace and the beach face.
foreshore
Sand on the seaward side of the berm, sloping toward the ocean, to the low tide mark.
fouling
Attachment or growth of marine organisms on underwater objects, usually objects that are made or introduced by humans.
fracture zone
Area of irregular, seismically inactive topography marking the position of a once-active transform fault.
Franklin, Benjamin
(1706-1790) American scientist and statesman. Published the first chart of an ocean current in 1769.
free wave
A progressive wave free of the forces that formed it. Compare to forced wave.
freezing point
The temperature at which a solid can begin to form as a liquid is cooled.
fringing reef
A coral reef that forms around the shore of an island and gradually extends out to sea.
fringing reef
A reef attached to the shore of a continent or island.
front
The boundary between two air masses of different density. The density differences can be caused by differences in temperature and/or humidity.
frontal storm
Precipitation and wind caused by the meeting of two air masses, associated with an extratropical cyclone. Generally, one air mass will slide over or under the other, and the resulting expansion of air will cause cooling and consequently, rain or snow.
frustule
Siliceous external cell wall of a diatom consisting of two interlocking valves fitted together like the halves of a box.
fucoxanthin
A brown or tan accessory pigment found in many species of brown algae and some species of diatoms.
fully developed sea
The theoretical maximum height attainable by ocean waves given wind of a specific strength, duration, and fetch. Longer exposure to wind will not increase the size of the waves.
gabbro
A coarse-grained, dark igneous rock, rich in iron and magnesium, the slow-cooling equivalent of basalt.
galaxy
A large rotating aggregation of stars, dust, gas and other debris held together by gravity. There are perhaps 50 billion galaxies in the universe and 50 billion stars in each galaxy.
gas bladder
In multicellular algae, an air-filled structure that assists in floatation.
gas exchange
Simultaneous passage, through a semipermeable membrane, of oxygen into an animal and carbon dioxide out of it.
Gastropoda
The class of phylum Mollusca that includes snails and sea slugs.
geographical equator
0° latitude, an imaginary line equidistant from the geographical poles.
geomorphology
Study of earth's land forms and the processes that have formed them.
geostrophic
Describing a gyre or current in balance between the Coriolis effect and gravity; literally, "turned by Earth".
geostrophic flow
Horizontal flow of water occurring when there is a balance between gravitation forces and the coriolis effect.
gill membrane
The thin boundary of living cells separating blood from water in a fish's (or other aquatic animal's) gills.
Global Positioning System (GPS)
Satellite-based navigation system that provides a geographical position -- longitude and latitude -- accurate to less than 1 meter.
Gondwanaland
An ancient landmass that fragmented to produce Africa, South America, Antarctica, Australia, and India.
GPS
Satellite-based navigation system that provides a geographical position -- longitude and latitude -- accurate to less than 1 meter.
grab sampler
Instrument used to remove a piece of the ocean floor for study.
graben
A portion of earth's crust that has moved downward and is bounded by steep faults; a rift.
granite
The relatively light crustal rock -- composed mainly of oxygen, silicon, and aluminum -- that forms the continents. Its density is about 2.7 g/cm3.
gravimeter
A sensitive device that measures variations in the pull of gravity at different places on Earth's surface.
gravity wave
A wave with wavelength greater than 1.73 centimeters (0.68 inch), whose restoring forces are gravity and momentum.
great circle
The intersection of a plane passing through the center of the earth with the surface of the earth. Great circles are formed by the equator and any two meridians of longitude 180° apart.
greenhouse effect
The warming of the lower layers of the atmosphere caused by the trapping of solar radiation by carbon dioxide and other gases.
greenhouse effect
Trapping of heat in the atmosphere. Incoming short-wavelength solar radiation penetrates the atmosphere, but the outgoing longer-wavelength radiation is absorbed by greenhouse gases and reradiated to Earth, causing a rise in surface temperature.
greenhouse gases
Gases in Earth's atmosphere that cause the greenhouse effect; include carbon dioxide, methane, and CFCs.
Greenwich Mean Theorem
(GMT) Solar time along the prime meridian passing through Greenwich, England; also known as Universal Time or Zulu Time.
groin
A short, artificial projection of durable material placed at a right-angle to a shore in an attempt to slow longshore transport of sand from a beach. Usually deployed in repeating units.
group velocity
Speed of advance of a wave train; for deep water waves, half the speed of individual waves within the group.
gulf
Part of the ocean or sea that is partly surrounded by land, usually on three sides. It is usually larger than a bay.
Gulf Stream
The strong western boundary current flowing the east coast of North America.
Gulf Stream
The strong western boundary current of the North Atlantic, off the Atlantic Coast of the United States.
guyot
A flat-topped seamount.
guyot
A flat-topped, submerged inactive volcano.
gyre
circuit of mid-latitude currents around the periphery of an ocean basin. Most oceanographers recognize five gyres plus the Antarctic Circumpolar Current.
habitat
The place where an individual or population of a given species lives. Its "mailing address".
hadal
The ocean zone below 19,680 feet.
hadal zone
The deepest zone of the ocean, below a depth of 5,000 meters (16,500 feet).
Hadley cell
The atmospheric circulation cell nearest the equator in each hemisphere. Air in these cells rises near the equator because of strong solar heating there and falls because of cooling at about 30° latitude. See also trade winds.
Hadley, George
(1685-1768) A London lawyer and philosopher who worked out the overall scheme of wind circulation in an effort to explain the trade winds.
half-life
Time required for one-half of all the unstable radioactive nuclei in a sample to decay.
halocline
The zone of the ocean in which salinity increases rapidly with depth. See also pycnocline.
Harmful Algal Bloom
(HAB) See red tide.
harmonic analysis
Process of separating astronomical tide-causing effects from the tide record, in order to predict the tides at any location.
Harrison, John
(1693-1776) British clockmaker who invented the modern chronometer in 1760.
heat
A form of energy produced by the random vibration of atoms or molecules.
heat budget
An expression of the total solar energy received on Earth during some period of time and the total heat lost from Earth by reflection and radiation into space during the same period.
heat capacity
The heat, measured in calories, required to raise 1 gram of substance 1 degree Celsius. The input of 1 calorie of heat energy raises the temperature of 1 gram of pure water by 1 degree.
Henry the Navigator
(1394-1460) Prince of Portugal who established a school for the study of geography, seamanship, shipbuilding, and navigation.
hermatypic
Describing coral species possessing symbiotic zooxanthellae within their tissues and capable of secreting calcium carbonate at a rate suitable for reef production.
heterotroph
An organism that derives nourishment from other organisms because it is unable to synthesize its own food molecules.
hierarchy
Grouping of objects by degrees of complexity, grade, or class. A hierarchical system of nomenclature is based on distinctions within groups and between groups.
high seas
That part of the ocean past the exclusive economic zone, which is considered common property to be shared by the citizens of the world. About 60% of the ocean area.
high tide
The maximum elevation reached by each rising tide.
high tide
The high-water position corresponding to a tidal crest.
high water
Maximum height reached by a rising tide.
high-energy coast
A coast exposed to large waves.
higher high water
Higher of the two high waters of any tidal day in a region of mixed tides.
higher low water
Higher of the two low waters of any tidal day in a region of mixed tides.
holdfast
The multi-branched structure anchoring seaweeds to hard surfaces.
holdfast
A complex branching structure that anchors many kinds of multicellular algae to the substrate.
holoplankton
Permanent members of the plankton community. Examples are diatoms and copepods. Compare to meroplankton.
Holothuroidea
The class of phylum Echinodermata to which sea cucumbers belong.
homeotherm
Organism with a body temperature that varies only within narrow limits.
hook
Spit turned landward at its outer end.
horse latitudes
Zones of erratic horizontal surface air circulation near 30°N and 30°S latitudes. Over land, dry air falling from high altitudes produces deserts at these latitudes (for example, the Sahara).
hot spot
A surface expression of a plume of magma rising from a stationary source of heat in the mantle.
hurricane
An intense tropical cyclone w/ winds that move counterclockwise around a low-pressure system.
hurricane
A large tropical cyclone in the North Atlantic or eastern Pacific, whose winds exceed 118 kilometers (74 miles) per hour.
hydrogen bond
Relatively weak bond formed between a partially positive hydrogen atom and a partially negative oxygen, fluorine, or nitrogen atom of an adjacent molecule.
hydrogenous sediment
Sediment precipitated from substances dissolved in water.
hydrogenous sediment
Sediment formed directly by precipitation from seawater. Also called authigenic sediment.
hydrologic cycle
Movement of water among the land, oceans, and atmosphere due to vertical and horizontal transport, evaporation, and precipitation.
hydrostatic pressure
The constant pressure of water around a submerged organism.
hydrothermal vent
A spring of superheated, mineral-rich water found on some ocean ridges.
hydrothermal vent
Spring of hot, mineral- and gas-rich seawater found on some oceanic ridges in zones of seafloor spreading.
hypertonic
Referring to a solution having a higher concentration of dissolved substances than the solution that surrounds it. Opposite of hypotonic.
hypocenter
See focus
hypothesis
A speculation about the natural world that may be verified or disproved by observation and experiment.
hypotonic
Referring to a solution having a lower concentration of dissolved substances than the solution that surrounds it. Opposite of hypertonic.
hypsographic curve
A graph of the area of the Earth's surface above any given elevation or depth above or below sea level.
ice age
One of several periods (lasting several thousand years each) of low temperature during the last million years. Glaciers and polar ice were derived from ocean water, lowering sea levels at least 100 meters (328 feet).
ice cap
Permanent cover of ice. Formally limited to ice atop land, but informally applied also to floating ice in the Arctic Ocean.
ice floe
A mass of firm sea ice floating as a unit.
ice pack
A large, floating expanse of broken ice masses pressed and frozen together.
iceberg
Floating piece of ice broken off from a glacier or ice sheet.
iceberg
Large mass of ice floating on the ocean that was formed on or adjacent to land. Tabular icebergs are tablelike or flat; pinnacled icebergs are castellated, or jagged. Southern icebergs are often tablular; northern icebergs are often pinnacled.
incidental catch
The portion of any catch or harvest taken in addition to the targeted species.
infauna
Animals that live buried in the sediment.
inlet
A passage giving the ocean access to an enclosed lagoon, harbor, or bay.
insolation rate
The amount of solar energy reaching Earth's surface per unit of time.
interference
Addition or subtraction of wave energy as waves interact. Also called resonance. See also constructive interference; destructive interference.
intermediate-depth water wave
A wave moving through water deeper than 1/20 but shallower than 1/2 its wavelength. Also called a transitional wave.
internal wave
A progressive wave occurring at the boundary between liquids of different densities.
international date line
An imaginary line through the Pacific Ocean roughly corresponding to 180° longitude, to the east of which, by international agreement, the calendar date is one day earlier than to the west.
intertidal volume
In an ambayment, the volume of water gained or lost owing to the rise and fall of the tide.
intertidal zone
The marine zone between the highest high-tide point on a shoreline and the lowest low-tide point. The intertidal zone is sometimes subdivided into four separate habitats by height above tidal datum, typically numbered 1 to 4, land to sea.
intertropical convergence zone (ITCZ)
The equatorial area at which the trade winds converge. The ITCZ usually lies at or near the meteorological equator. Also called the doldrums.
inverse estuary
An ambayment, often located in arid climates, with high evaporating and little freshwater input. Circulation is seaward at depth and inward at the surface, opposite that of a typical estuary. Salinity is generally higher than average seawater salinities.
invertebrate
Animal lacking a backbone.
ion
An atom (or small group of atoms) that becomes electrically charged by gaining or losing one or more electrons.
ionic bond
A chemical bond resulting from attraction between oppositely charged ions. These forces are said to be "electrostatic" in nature.
ionizing radiation
Fast-moving particles or high-energy electromagnetic radiation emitted as unstable atomic nuclei disintegrate. The radiation has enough energy to dislodge one or more electrons from atoms it hits to form charged ions, which can react with and damage living tissue.
island arc
Curving chain of volcanic islands and seamounts almost always found paralleling the concave edge of a trench.
isobar
Line of equal, or constant, pressure
isobath
Contour of constant depth.
isohaline
Having a uniform salt content.
isopleth
Line of equal density
isopycnal
Having a uniform density.
isostasy
The equilibrium of the earth's crust, a condition in which the forces tending to elevate balance those tending to depress; the state in which pressures from every side are equal
isostasy
Mechanism by which areas of earth's crust rise or subside until their masses are in balance, "floating" on the mantle.
isostatic equilibrium
Balanced support of lighter material in a heavier, displaced supporting matrix. Analogous to buoyancy in a liquid.
isotherm
Line of equal temperature
isothermal
Having a uniform temperature.
isotonic
Referring to a solution having the same concentration of dissolved substances as the solution that surrounds it.
ITCZ
Intertropical convergence zone; The equatorial area at which the trade winds converge. The ITCZ usually lies at or near the meteorological equator. Also called the doldrums.
Jason-1
A follow-on satellite mission to TOPEX/Poseidon.
jellyfish
(sea jelly) semitransparent, bell-shaped pelagic organism, often with long tentacles bearing stinging cells.
jet stream (polar)
A stream of air, between 30 and 50° N and S and about 12 km above earth, moving from west to east at an average speed of 1 km/h.
jetty
Structure located to influence currents or to protect the entrance to a harbor or river from waves.
kelp
Informal name for any species of large phaeophyte.
kelps
Group of large, fast-growing brown seaweeds.
kingdom
The largest category of biological classification. Five kingdoms are presently recognized.
knot
A speed of 1 nautical mile per hour. See also nautical mile: the length of 1 minute of latitude, 6,076 feet, 1.15 statute miles, or 1.85 kilometers..
krill
Euphausia superba, a thumb-size crustacean common in Antarctic waters.
La Niña
The periodic cooling of the surface waters in the eastern Pacific.
La Niña
An event during which normal tropical Pacific atmospheric and oceanic circulation strengthens and the surface temperature of the eastern South Pacific drops below average values. Usually occurs at the end of an ENSO event. See also ENSO.
lag deposits
Large particles left on a beach after the smaller particles are washed away.
lagoon
A shallow body of water, such as a pond or lake, usually connected to the sea.
lagoon
A shallow body of seawater generally isolated from the ocean by a barrier island. Also, the body of water enclosed within an atoll, or the water within a reverse estuary.
land breeze
Movement of air offshore as marine air heats and rises.
langmuir cells
Shallow wind-driven circulation; paired helixes of moving water from windows of debris along convergence lines.
latent heat of fusion
Heat removed from a liquid during freezing (or added to a solid during thawing) that produces a change in state but not a change in temperature. For pure water, 80 calories per gram at 0°C (32°F).
latent heat of vaporization
Heat added to a liquid during evaporation (or released from a gas during condensation) that produces a change in state but not a change in temperature. For pure water, 585 calories per gram at 20°C (68°F).
lateral-line system
A system of sensors and nerves in the head and midbody of fishes and some amphibians that functions to detect low-frequency vibrations in water.
latitude
A measure of north-south location, relative to the equator at 0˚.
latitude
Regularly spaced imaginary lines on Earth's surface running parallel to the equator.
Laurasia
An ancient landmass that fragmented to produce North America and Eurasia.
lava coast
A primary coast formed by active volcanism producing laval flows that extend to the sea.
law
A large construct explaining events in nature that have been observed to occur with unvarying uniformity under the same conditions.
Law of the Sea
Collective term for laws and treaties governing the commercial and practical use of the ocean.
leading margin
Also known as active margin. The edge of the overriding plate at a trench or subduction zone.
lee
Shelter; the part or side sheltered from wind or waves.
Library of Alexandria
The greatest collection of writings in the ancient world, founded in the third century BC by Alexander the Great. Could be considered the first university.
light
Electromagnetic radiation propagated as small, nearly massless particles that behave like both a wave and a stream of particles.
limiting factor
A physical or biological environmental factor whose absence or presence in an inappropriate amount limits the normal actions of an organism.
Linnaeus, Carolus
Carl von Linné (1707-1778). Swedish 'father' of modern taxonomy.
lithification
Conversion of a sediment into sedimentary rock by pressure or by the introduction of a mineral cement.
lithosphere
The brittle, relatively cool outer layer of earth, consisting of the oceanic and the continental crust and the outermost, rigid layer of mantle.
littoral
Area of the shore between mean high water and mean low water; the intertidal zone.
littoral zone
Seashore between high and low tide.
littoral zone
The band of coast alternately covered and uncovered by tidal action; the intertidal zone.
longitude
A measure of east-west location relative to the Prime Meridian that runs through the Greenwich Observatory, London, UK.
longitude
Regularly spaced imaginary lines on Earth's surface running North and South and converging at the poles.
longshore bar
A submerged or exposed line of sand lying parallel to shore and accumulated by wave action.
longshore current
A current running parallel to shore in the surf zone, caused by the incomplete refraction of waves approaching the beach at an angle.
longshore drift
The movement of beach material parallel to the coastline by combined wind and wave action.
longshore drift
Movement of sediments parallel to shore, driven by wave energy.
longshore trough
Submerged excavation parallel to shore adjacent to an exposed sandy beach. Caused by the turbulence of water returning to the ocean after each wave.
loran
Navigational system in which position is determined by measuring the difference in time of reception of synchronized radio signals; derived from the phrase "long-range navigation."
low tide
The minimum elevation reached by each falling tide.
low tide
The low-water position corresponding to a tidal trough.
low tide terrace
The smooth, hard-packed beach seaward of the beach scarp on which waves expend most of their energy. Site of the most vigorous onshore and offshore movement of sand.
low water
Lowest elevation reached by a falling tide.
low-energy coast
A coast only rarely exposed to large waves.
lower high water
The lower of the two high waters of any tidal day in a region of mixed tides.
lower low water
The lower of the two low waters of any tidal day in a region of mixed tides.
lower mantle
The rigid portion of Earth's mantle below the asthenosphere.
lunar month
Time required for the moon to pass from one new moon to another new moon (approx. 29 days)
lunar tide
Tide caused by gravitational and inertial interaction of the moon and Earth.
lysocline
Depth at which calcareous skeletal material first begins to dissolve.
macroplankton
Animal plankters larger than 1 to 2 centimeters ( 1/2 to 1 inch). An example is the jellyfish.
Magellan, Ferdinand
(c. 1480-1521) Portuguese navigator in the service of Spain who led the first expedition to navigate the Earth, 1519-22. He was killed in the Philippines.
magma
Molten rock found below Earth's crust that is ejected by volcanoes and emerges at ocean ridges as lava.
magma
Molten rock capable of fluid flow. Called lava above ground.
magnetometer
A device that measures the amount and direction of residual magnetism in a rock sample.
Mammalia
The class of animals.
manganese nodules
Rounded, layered lumps found on the deep-ocean floor that contain on average about 18% manganese, 17% iron, with smaller amounts of nickel, cobalt, and copper and traces of two dozen other metals; a hydrogenous sediment.
mangrove
Flowering shrubs and trees tolerant of seawater, found on low-lying tropical coasts and estuaries
mangrove
Large flowering shrub or tree that grows in dense thickets or forests along muddy or silty tropical coasts.
mantle
The layer of Earth between the crust and the core.
mantle
The layer of Earth between the crust and the core; composed of silicates of iron and magnesium. The mantle has an average density of about 4.5 gm/cm3 and accounts for about 68% of the Earth's mass.
map
A representation of Earth's surface, usually depicting mostly land areas. See also chart.
mariculture
The farming of marine organisms, usually in estuaries, bays, or nearshore environments or in specially designed structures using circulating seawater. Compare aquaculture: The growing or farming of plants and animals in a water environment under controlled conditions.
marine energy resource
Any resource resulting from the direct extraction of energy from the heat or movement of ocean water.
marine pollution
The introduction by humans of substances or energy into the ocean that changes the quality of the water or affects the physical or biological environment.
marine science
The process (or result) of applying scientific method to the ocean, its surroundings, and the life forms within it. Also called oceanography or oceanology.
masking pigment
One of the class of pigments (such as fucoxanthin, phycobilin, and xanthophyll) present in various photosynthetic plants and that assist in the absorption of light and the transfer of its energy to chlorophyll. Also called accessory pigment.
mass
A measure of the quantity of matter.
mass extinction
A catastrophic, global event in which major species perish abruptly.
Maury, Matthew
(1806-1873) "Father" of physical oceanography. Probably the first person to undertake the systemic study of the ocean as a full-time occupation, and probably the first to understand the global interlocking of currents, wind flow, and weather.
maximum sustainable yield
The maximum amount of fish, crustaceans, and mollusks that can be caught without impairing future populations.
mean earth sphere depth
The depth below sea level of the surface of the solid earth if it was perfectly smooth with no variation in elevation. This is 2403 m (7884 ft) below present sea level.
mean lower low water
The arithmetic mean of the lesser of a daily pair of low waters, observed over a specific 19 year cycle called the national tidal datum epoch.
mean ocean sphere depth
The depth of the ocean if the solid earth was perfectly smooth with no variation in elevation. This is 2646m (8642 ft.)
mean sea level
The height of the ocean surface averaged over a few year's time.
meander
Turn or winding curve of a current.
medusa
Free-swimming body form of many members of the phylum Cnidaria.
meiobenthos
Very small animals living buried in the sediments of the sea floor.
membrane
A complex structure of proteins and lipids that forms boundaries around and within the cell. It is usually semipermeable, allowing some kinds of molecules to pass through but not others.
mercator projection
A map projection in which the surface of earth is projected onto a cylinder. Distortion is great at high latitudes and the poles cannot be shown. Mercator projections are frequently used for navigation because a straight line drawn on them is a line of true direction or constant compass heading.
meridian
Circle of longitude passing through the poles and any given point on earth's surface.
meroplankton
The planktonic phase of the life cycle of organisms that spend only part of their life drifting in the plankton. Compare to holoplankton.
mesoderm
The middle layer of cells in a developing embryo.
mesopelagic
Oceanic zone from 200-1000m.
mesosphere
The rigid inner mantle, similar in a chemical composition to the asthenosphere.
metabolic rate
The rate at which energy-releasing reactions proceed within an organism.
metamerism
Segmentation; repeating body parts.
Meteor Expedition
German Atlantic expedition begun in 1925; the first to use an echo sounder and other modern electrical and electronic instrumentation.
meteorological equator
The irregular imaginary line of thermal equilibrium between hemispheres. It is situated about 5° north of the geographical equator, and its position changes with the seasons, moving slightly north in northern summer. Also called the thermal equator.
meteorological tide
A tide influenced by the weather. Arrival of a storm surge will alter the estimate of a tide's height or arrival time, as will a strong, steady onshore or offshore wind.
metrophagy
Tendency for large reptiles to eat entire cities.
microbial loop
Component of marine food webs in which dissolved organic material cycles through bacteria and nanoplankton then back to small members of the zooplankton.
microplankton
Net plankton, composed of individuals from 0.07-1 mm in size but not large enough to be retained by a small mesh net.
microtektite
Translucent oblong particles of glass, a component of cosmogenous sediment.
mid-ocean ridge
A region of the ocean floor where magma rises to the surface to create new ocean floor on either side of a central rift valley.
Milky Way
The name of our galaxy. Sometimes applied to the field of stars in our home spiral arm, which is correctly called the Orion arm.
mineral
A naturally occurring inorganic crystalline material with a specific chemical composition and structure.
minus tide
Low tide level below the mean value of the low tides or the zero tidal depth reference.
mitigation
Coastal management concept requiring developers to replace developed areas with equivalent natural areas or to reengineer other areas to resemble areas prior to development.
mixed layer
The upper layer of ocean in which temperature and salinity are relatively constant with depth. Depending on local conditions, the surface zone may reach to 1,000 meters (3,300 feet) or be absent entirely. Also called the surface zone.
mixed tide
A complex tidal cycle, usually with two high tides and two low tides of unequal height per day.
mixing time
The time necessary to mix a substance through the ocean, about 1,600 years.
mixture
A close intermingling of different substances that still retain separate identities. The properties of a mixture are heterogenous; they may vary within the mixture.
mohorovicic discontinuity
(moho) Boundary between crust and mantle, marked by a rapid increase in seismic wave speed.
molecule
A group of atoms held together by chemical bonds. The smallest unit of a compound that retains the characteristic of the compound.
Mollusca
The phylum of animals that includes chitons, snails, clams, and octupuses.
molt
To shed an external covering.
monoculture
Cultivation of only one species of organism in an aquaculture system.
monsoon
A pattern of wind circulation that changes with the season. Also, the rainy season in areas with monsoon wind patterns.
moon tide
Tide caused by gravitational and inertial interaction of the moon and Earth. Also called lunar tide.
moon tide
Portion of the tide generated solely by the moon's tide-raising force, as distinguished from that of the sun.
moraine
Hills or ridges of sediment deposited by glaciers.
motile
Able to move about.
multicellular
Consisting of more than one cell.
multicellular algae
Algae with bodies consisting of more than one cell. Examples are kelp and ulva.
mutation
A heritable change in an organism's genes.
mutualism
A symbiotic interaction between two species that is beneficial to both.
Mysticeti
The suborder of baleen whales.
nanoplankton
Very small members of the plankton community. Examples are coccolithophores and silicoflagellates.
Nansen bottle
A water sampling instrument invented in 1910 by the Norwegian scientist and explorer Fridtjoj Nansen.
natural selection
A mechanism of evolution that results in the continuation of only those forms of life best adapted to survive and reproduce in their environment.
natural system of classification
A method of classifying an organism based on its ancestry or origin.
nautical chart
A chart used for marine navigation.
nautical mile
The length of 1 minute of latitude, 6,076 feet, 1.15 statute miles, or 1.85 kilometers.
nautical mile
The length of 1 minute of latitude, 6,076 feet, 1.15 statute miles, or 1.85 kilometers.
navigation
The science of position fixing and course plotting, using astronomical and other observations.
neap tide
The time of smallest variation between high and low tides occurring when Earth, moon, and sun align at right angles. Neap tides alternate with spring tides, occurring at two week intervals.
neap tides
Tides with much smaller ranges than spring tides, that occur while the gravitational pulls of the moon and sun on the oceans work against each other.
nebula
Diffuse cloud of dust and gas.
nekton
Drifting organisms.
Nematoda
The phylum of animals to which roundworms belong.
neritic
Of the shore or coast. Refers to continental margins and the water covering them, or to nearshore organisms.
neritic sediment
Continental shelf sediment consisting primarily of terrigenous material.
neritic zone
The zone of open water near shore, over the continental shelf.
neritic zone
Zone from high tide to the continental shelf break.
net circulation
The long-term transport of water out of an estuary at the surface and into the estuary at depth averaged over many tidal cycles.
niche
Description of an organism's functional role in a habitat. Its "job".
node
The line or point of no wave action in a standing pattern. See also amphidromic point: A "no-tide" point in an ocean caused by basin resonances, friction, and other factors around which tide crests rotate. About a dozen amphidromic points exist in the world ocean.
nodule
Solid mass of hydrogenous sediment, most commonly manganese or ferromanganese nodules and phosphorite nodules.
nonconservative constituent
An element whose proportion in seawater varies with time and place, depending on biological demand or chemical reactivity. An element with a short residence time. For example, iron, aluminum, silicon, trace nutrients, dissolved oxygen, and carbon dioxide.
nonconservative resource
Any use of the ocean in place, such as transportation of people and commodities by sea, recreation, or waste disposal.
nonrenewable resource
Any resource that is present on Earth in fixed amounts and cannot be replenished.
nonvascular
Describing photosynthetic autotrophs without vessels for the transport of fluid. Examples are algae.
nor'easter (northeaster)
Any energetic extratropical cyclone that sweeps the eastern seaboard of North America in winter.
North Atlantic Deep Water
Cold, dense water formed in the Arctic that flows onto the floor of the North Atlantic ocean.
notochord
Stiffening structure found at some time in the life cycle of all members of the Phylum Chordata.
nuclear energy
Energy released when atomic nuclei undergo a nuclear reaction such as the spontaneous emission of radioactivity, nuclear fission, or nuclear fusion. About 17% of the electrical power generated in the United States is provided by the nuclear fission of uranium in civilian power reactors.
nudibranches
Soft-bodied, gastropod mollusks; sea slugs.
nutrient
Any needed substance that an organism obtains from its environment except oxygen, carbon dioxde, and water.
ocean
1) The great body of saline water that covers 70.78% of the surface of Earth. 2) One of its primary subdivisions, bounded by continents, the equator, and other imaginary lines.
ocean
One of the five great bodies of seawater defined by continental margins, the equator, and other arbitrary divisions.
ocean basin
Deep-ocean floor made of basaltic crust. Compare continental margin: The submerged outer edge of a continent, made of granitic crust. Includes the continental shelf and continental slope.
oceanic crust
The outermost solid surface of Earth beneath ocean floor sediments, composed primarily of basalt.
oceanic ridge
Young seabed at the active spreading center of an ocean, often unmasked by sediment, bulging above the abyssal plain. The boundary between diverging plates. Often called a mid-ocean ridge, though less than 60% of the length exists at mid-ocean.
oceanic zone
The zone of open water away from shore, past the continental shelf.
oceanography
The science of the ocean. See also marine science: The process (or result) of applying scientific method to the ocean, its surroundings, and the life forms within it.
oceanography
The scientific study of all aspects of the ocean.
oceanus
Latin form of okeanos, the Greek name for the "ocean river" past Gibraltor.
Odontoceti
The suborder of toothed whales.
offshore
Direction seaward of the shore.
onshore
Direction toward the shore.
oolite sand
Hydrogenous sediment formed when calcium carbonate precipitates from warmed seawater as pH rises, forming rounded grains around a shell fragment or other particle.
oolith
Small, rounded, accretionary body of calcium carbonate. Created by precipitation of calcium carbonate in shallow, warm seawater due to a change in water temperature or acidity.
ooze
Sediment of at least 30% biological origin.
ophiolite
An assemblage of subducting oceanic lithosphere scraped off (obducted) onto the edge of a continent.
Ophiuroidea
The class of the phylum Echinodermata to which brittle stars belong.
orbit
In ocean waves, the circular pattern of water particle movement at the air-sea interface. Orbital motion contrasts with the side-to-side or back-and-forth motion of pure transverse or longitudinal waves.
orbital inclination
The 23°27´ "tilt" of Earth's rotational axis relative to the plane of its orbit around the sun.
orbital wave
A progressive wave in which particles of the medium move in closed circles.
orographic effect
Precipitation patterns caused by the flow of air over mountains.
osmoregulation
The ability to adjust internal salt concentration.
osmoregulation
The regulation of the concentration of body fluids by aquatic animals.
osmosis
The diffusion of water from a region of high water concentration to a region of lower water concentration through a semipermeable membrane.
osmotic pressure
Pressure that builds up in a confined fluid because of osmosis.
Osteichthyes
The class of fishes with bony skeletons.
outgassing
The volcanic venting of volatile substances.
overfishing
Harvesting so many fish that there is not enough breeding stock left to replenish the species.
overfishing
The commercial fishing of natural populations so that breeding does not replenish what has been removed.
overturn
Sinking of denser water and its replacement by less-dense water from below.
oxygen minimum zone
A zone in which oxygen is depleted by animals and not replaced by phytoplankton.
oxygen revolution
The time span, from about 2 billion to 400 million years ago, during which photosynthetic autotrophs changed the composition of Earth's atmosphere to its current oxygen-rich mixture.
ozone
O3, the triatomic form of oxygen. Ozone in the atmosphere protects living things from some of the harmful effects of the sun's ultraviolet radiation.
ozone layer
A diffuse layer of ozone mixed with other gases surrounding the world at a height of about 20 to 40 kilometers (12 to 25 miles).
Pacific Ring of Fire
The zone of seismic and volcanic activity that encircles the Pacific Ocean.
pack ice
Sea ice that forms around the permanent ice sheets of polar regions in winter and which thins and retreats in the summer.
paleoceanography
The study of the ocean's past.
paleomagnetism
The "fossil", or remanent, magnetic field of a rock.
Pangaea
Name given by Alfred Wegener to the original "protocontinent". The breakup of Pangaea gave rise to the Atlantic Ocean and to the continents we see today.
Panthalassa
Name given by Alfred Wegener to the ocean surrounding Pangaea.
parasitism
A symbiotic relationship in which one species spends all or part of its life cycle on or within another, using the host species (or food within the host) as a source of nutrients. The most common form of symbiosis.
partially mixed estuary
An estuary in which an influx of seawater occurs beneath a surface layer of fresh water flowing seaward. Mixing occurs along the junction.
passive margin
Continental margin near an area of lithospheric plate divergence. Also called Atlantic-type margin.
passive sonar
A device that detects the intensity and direction of underwater sounds.
PCBs
Polychlorinated biphenyls. Chlorinated hydrocarbons once widely used to cool and insulate electrical devices and to strengthen wood or concrete. PCBs may be responsible for the changes in and declining fertility of some marine mammals.
pelagic
Of the open ocean. Refers to the water above the deep-ocean basins, sediments of oceanic origin, or organisms of the open ocean.
pelagic sediment
Sediments of the slope, rise, and deep-ocean floor that originate in the ocean.
pelagic zone
The realm of open water. See also benthic zone: the seabed.
pelagic zone
The water column.
Perigean Tide
A monthly tide of increased range that occurs when the moon is closest to earth (at perigee).
perigee
The point in the orbit of a satellite where it is closest to the main body; opposite of apogee.
perihelion
The point in the orbit of a satellite where it is closest to the sun; opposite of aphelion.
period
See wave period: the time it takes for successive wave crests to pass a fixed point.
pH scale
A measure of the acidity or alkalinity of a solution. Numerically, the negative logarithm of the concentration of hydrogen ions in an aqueous solution. A pH of 7 is neutral; lower numbers indicate acidity, and higher numbers indicate alkalinity.
Phaeophyta
Brown multicellular algae, including kelps.
phosphorite
A sedimentary rock composed largely of calcium phosphate and largely in the form of concretions and nodules.
photic zone
The thin film of lighted water at the top of the world ocean. The photic zone rarely extends deeper than 200 meters (660 feet). Compare euphotic zone: The upper layer of the photic zone in which net photosynthetic gain occurs. Part of the photic zone, which is the thin film of lighted water at the top of the world ocean.
photic zone
The thin film of lighted water at the top of the world ocean. The photic zone rarely extends deeper than 200 meters (660 feet). See also euphotic zone.
photo cell
A device that converts light energy to electrical energy; used to determine solar radiation below the sea surface.
photon
The smallest unit of light energy.
photophore
Luminous organ found on fish.
photosynthesis
The process by which autotrophs bind light energy into the chemical bonds of food with the aid of chlorophyll and other substances. The process uses carbon dioxide and water as raw materials and yields glucose and oxygen.
phycobilin
A reddish accessory pigment found in red algae.
phylum
One of the major groups of the animal kingdom whose members share a similar body plan, level of complexity, and evolutionary history. (Plural: phyla) (The major groups of the plant kingdom are called divisions.)
physical factor
An aspect of the physical environment that affects living organisms, such as light, salinity, or temperature.
physical resource
Any resource that has resulted from the deposition, precipitation, or accumulation of a useful nonliving substance in the ocean or seabed. Also called a nonliving resource.
physiographic map
Portrayal of earth's features by perspective drawing.
phytoplankton
Plantlike, usually single-celled members of the plankton community.
picoplankton
Extremely small members of the plankton community, typically 0.2 to 2 micrometers ( 4 to 40 millionths of an inch) across.
Pinnipedia
The carnivoran suborder that contains the seals, sea lions, and walruses.
pinnipeds
The seals, walruses, and sea lions.
piston corer
A seabed-sampling device capable of punching through up to 25 meters (80 feet) of sediment and returning an intact plug of material.
planet
A smaller, usually nonluminous body orbiting a star.
plankter
Informal name for a member of the plankton community.
plankton
Drifting or weakly swimming organisms suspended in water. Their horizontal position is to a large extent dependent on the mass flow of water than on their own swimming efforts.
plankton bloom
A sudden increase in the number of phytoplankton cells in a volume of water.
plankton net
Conical net of fine nylon or Dacron fabric used to collect plankton.
Plantae
The kingdom to which multicellular vascular autotrophs belong.
plate
One of about a dozen rigid segments of Earth's lithosphere that move independently. The plate consists of continental or oceanic crust and the cool, rigid upper mantle directly below the crust.
plate tectonics
The theory that Earth's lithosphere is fractured into plates, which move relative to each other and are driven by convection currents in the mantle. Most volcanic and seismic activity occurs at plate margins.
plate tectonics
The processes by which the plates that form Earth's surface are formed, moved, and destroyed.
Platyhelminthes
The phylum of animals to which flatworms belong.
plunging wave
Breaking wave in which the upper section topples forward and away form the bottom, forming an air-filled tube.
poikilotherm
Organism with a body temperature that varies according to the temperature of surroundings.
polar cell
The atmospheric circulation cell centered over each pole.
polar easterlies
Winds blowing from the poles toward approximately 60°N and 60°S; winds are northeasterly in the north hemisphere and southeasterly in the south hemisphere.
polar front
Boundary between the polar cell and the Ferrell cell in each hemisphere.
polar molecule
A molecule with unbalanced charge. One end of the molecule has a slight negative charge, and the other end has a slight positive charge.
polar ocean areas
Zones to the south of the Antarctic Convergence and to the north of the Arctic Convergence.
polar regions
The cold zones between the poles and either the Arctic or Antarctic circles.
polar reversal
The periodic reversal of earth's magnetic field where the north magnetic pole becomes the south magnetic pole and vice versa.
polar wandering curve
A plot of the apparent location earth's north magnetic pole as a function of geologic time.
pollutant
A substance that causes damage by interfering directly or indirectly with an organism's biological processes.
pollutant
A harmful substance or heat energy introduced into an ecosystem by human activities.
Pacific Ring of Fire
The zone of seismic and volcanic activity that encircles the Pacific Ocean.
pack ice
Sea ice that forms around the permanent ice sheets of polar regions in winter and which thins and retreats in the summer.
paleoceanography
The study of the ocean's past.
paleomagnetism
The "fossil", or remanent, magnetic field of a rock.
Pangaea
Name given by Alfred Wegener to the original "protocontinent". The breakup of Pangaea gave rise to the Atlantic Ocean and to the continents we see today.
Panthalassa
Name given by Alfred Wegener to the ocean surrounding Pangaea.
parasitism
A symbiotic relationship in which one species spends all or part of its life cycle on or within another, using the host species (or food within the host) as a source of nutrients. The most common form of symbiosis.
partially mixed estuary
An estuary in which an influx of seawater occurs beneath a surface layer of fresh water flowing seaward. Mixing occurs along the junction.
passive margin
Continental margin near an area of lithospheric plate divergence. Also called Atlantic-type margin.
passive sonar
A device that detects the intensity and direction of underwater sounds.
PCBs
Polychlorinated biphenyls. Chlorinated hydrocarbons once widely used to cool and insulate electrical devices and to strengthen wood or concrete. PCBs may be responsible for the changes in and declining fertility of some marine mammals.
pelagic
Of the open ocean. Refers to the water above the deep-ocean basins, sediments of oceanic origin, or organisms of the open ocean.
pelagic sediment
Sediments of the slope, rise, and deep-ocean floor that originate in the ocean.
pelagic zone
The realm of open water. See also benthic zone: the seabed.
pelagic zone
The water column.
Perigean Tide
A monthly tide of increased range that occurs when the moon is closest to earth (at perigee).
perigee
The point in the orbit of a satellite where it is closest to the main body; opposite of apogee.
perihelion
The point in the orbit of a satellite where it is closest to the sun; opposite of aphelion.
period
See wave period: the time it takes for successive wave crests to pass a fixed point.
pH scale
A measure of the acidity or alkalinity of a solution. Numerically, the negative logarithm of the concentration of hydrogen ions in an aqueous solution. A pH of 7 is neutral; lower numbers indicate acidity, and higher numbers indicate alkalinity.
Phaeophyta
Brown multicellular algae, including kelps.
phosphorite
A sedimentary rock composed largely of calcium phosphate and largely in the form of concretions and nodules.
photic zone
The thin film of lighted water at the top of the world ocean. The photic zone rarely extends deeper than 200 meters (660 feet). Compare euphotic zone: The upper layer of the photic zone in which net photosynthetic gain occurs. Part of the photic zone, which is the thin film of lighted water at the top of the world ocean.
photic zone
The thin film of lighted water at the top of the world ocean. The photic zone rarely extends deeper than 200 meters (660 feet). See also euphotic zone.
photo cell
A device that converts light energy to electrical energy; used to determine solar radiation below the sea surface.
photon
The smallest unit of light energy.
photophore
Luminous organ found on fish.
photosynthesis
The process by which autotrophs bind light energy into the chemical bonds of food with the aid of chlorophyll and other substances. The process uses carbon dioxide and water as raw materials and yields glucose and oxygen.
phycobilin
A reddish accessory pigment found in red algae.
phylum
One of the major groups of the animal kingdom whose members share a similar body plan, level of complexity, and evolutionary history. (Plural: phyla) (The major groups of the plant kingdom are called divisions.)
physical factor
An aspect of the physical environment that affects living organisms, such as light, salinity, or temperature.
physical resource
Any resource that has resulted from the deposition, precipitation, or accumulation of a useful nonliving substance in the ocean or seabed. Also called a nonliving resource.
physiographic map
Portrayal of earth's features by perspective drawing.
phytoplankton
Plantlike, usually single-celled members of the plankton community.
picoplankton
Extremely small members of the plankton community, typically 0.2 to 2 micrometers ( 4 to 40 millionths of an inch) across.
Pinnipedia
The carnivoran suborder that contains the seals, sea lions, and walruses.
pinnipeds
The seals, walruses, and sea lions.
piston corer
A seabed-sampling device capable of punching through up to 25 meters (80 feet) of sediment and returning an intact plug of material.
planet
A smaller, usually nonluminous body orbiting a star.
plankter
Informal name for a member of the plankton community.
plankton
Drifting or weakly swimming organisms suspended in water. Their horizontal position is to a large extent dependent on the mass flow of water than on their own swimming efforts.
plankton bloom
A sudden increase in the number of phytoplankton cells in a volume of water.
plankton net
Conical net of fine nylon or Dacron fabric used to collect plankton.
Plantae
The kingdom to which multicellular vascular autotrophs belong.
plate
One of about a dozen rigid segments of Earth's lithosphere that move independently. The plate consists of continental or oceanic crust and the cool, rigid upper mantle directly below the crust.
plate tectonics
The theory that Earth's lithosphere is fractured into plates, which move relative to each other and are driven by convection currents in the mantle. Most volcanic and seismic activity occurs at plate margins.
plate tectonics
The processes by which the plates that form Earth's surface are formed, moved, and destroyed.
Platyhelminthes
The phylum of animals to which flatworms belong.
plunging wave
Breaking wave in which the upper section topples forward and away form the bottom, forming an air-filled tube.
poikilotherm
Organism with a body temperature that varies according to the temperature of surroundings.
polar cell
The atmospheric circulation cell centered over each pole.
polar easterlies
Winds blowing from the poles toward approximately 60°N and 60°S; winds are northeasterly in the north hemisphere and southeasterly in the south hemisphere.
polar front
Boundary between the polar cell and the Ferrell cell in each hemisphere.
polar molecule
A molecule with unbalanced charge. One end of the molecule has a slight negative charge, and the other end has a slight positive charge.
polar ocean areas
Zones to the south of the Antarctic Convergence and to the north of the Arctic Convergence.
polar regions
The cold zones between the poles and either the Arctic or Antarctic circles.
polar reversal
The periodic reversal of earth's magnetic field where the north magnetic pole becomes the south magnetic pole and vice versa.
polar wandering curve
A plot of the apparent location earth's north magnetic pole as a function of geologic time.
pollutant
A substance that causes damage by interfering directly or indirectly with an organism's biological processes.
pollutant
A harmful substance or heat energy introduced into an ecosystem by human activities.
Polychaeta
The largest and most diverse class of phylum Annelida. Nearly all polychaetes are marine.
polychlorinated biphenyls
Chlorinated hydrocarbons once widely used to cool and insulate electrical devices and to strengthen wood or concrete. PCBs may be responsible for the changes in and declining fertility of some marine mammals.
polyculture
Cultivation of more than one species of organism in an aquaculture system.
polyna
A gap in polar pack ice at which liquid water contacts the atmosphere.
Polynesia
A large group of Pacific Islands extending from the Hawaiian Islands south to New Zealand and east to Easter Island.
polyp
One of two body forms of Cnidaria. Polyps are cup shaped and possess rings of tentacles. Coral animals are polyps.
Polyplacophora
The class of the phylum Mollusca that includes the chitons.
poorly sorted sediment
A sediment in which particles of many sizes are found.
population
A group of individuals of the same species occupying the same area.
population density
The number of individuals per unit area.
Porifera
The phylum of animals to which sponges belong.
potable water
Water suitable for drinking.
precipitate
(1) A solid substance formed in an aqueous reaction. (2) The process by which a solute forms in and falls from a solution. The falling of water or ice from the atmosphere.
precipitation
Liquid or solid water that falls from the air and reaches the surface as rain, hail, or snowfall.
precision depth recorder
(PDR) Instrument used to obtain continuous pictorial record of the ocean bottom by timing the returning echoes of sound pulses.
predator
An animal that feeds by capturing and eating other animals.
pressure
Force per unit area.
prey
An organism consumed by a predator.
primary coast
Coast on which terrestrial influences dominate. See also secondary coast: a coast dominated by marine processes.
primary consumer
Initial consumer of primary producers. The consumers of autotrophs; the second level in food webs.
primary forces
The forces that induce and maintain water flow in ocean systems: thermal expansion, wind friction, and density differences.
primary producer
An organism capable of using energy from light or energy-rich chemicals in the environment to produce energy-rich organic compounds. An autotroph.
primary production
The biological conversion of inorganic carbon (carbon dioxide) into living material (organic carbon)
primary productivity
The synthesis of organic materials from inorganic substances by photosynthesis or chemosynthesis. Expressed in grams of carbon bound into carbohydrate per unit area per unit of time (g C/m2/yr).
prime meridian
Meridian of 0° longitude, used as the origin for measurements of longitude; internationally accepted as the meridian of the Royal Naval Observatory, Greenwich, England.
Prince Henry the Navigator
Established a center at Sagres, Portugal, for the study of marine science and navigation in the mid-1450's.
principle of constant proportions
The proportions of major conservative elements in seawater remain nearly constant, though total salinity may change with location. Also called Forchhammer's principle.
principle of constant proportions
The proportions of major conservative elements in seawater remain nearly constant, though total salinity may change with location Also called Forchhammer's principle.
progressive wave
A wave of moving energy in which the wave form moves in one direction along the surface (or junction) of the transmission medium (or media).
projection
The system used to translate the three-dimensional form of Earth onto a two-dimensional map.
projection
A system of projecting lines of latitude and longitude onto a plain surface to create a map with specific physical properties.
Protista
The kingdom of single-celled nucleated organisms to which protozoa, diatoms, and dinoflagellates belong. Also called Protoctista.
proton
A positively charged particle at the center of an atom.
protostar
Tightly condensed knot of material that has not yet attained fusion temperature.
protozoa
Multiphyletic animal group within the kingdom Protista. Protozoa include amoebas, paramecia, foraminiferans, and radiolarians.
pseudopodium
Flowing, temporary extension of the protoplasm of a cell, used in locomotion or feeding.
radar
Radio Detection and Ranging- the use of pulsed radio waves to follow moving objects by analyzing changes in reflected radio signals.
rafting
Transport of sediment, rock, silt, and other land matter out to sea by ice, logs, and the like, with the deposition of the rafted material when the carrying agent melts or disintegrates.
rain shadow
An area of low precipitation on the leeward (or sheltered) side of an island or mountain. Precipitation occurs on the windward side as the air is forced to ascend the side of the island or mountain so the descending air on the leeward side is dry.
red clay
Red to brown fine-grained lithogenous deposit, of predominantly clay size, which is derived from land, transported by winds and currents, and deposited far from land and at a great depth; also known as brown mud or brown clay.
red tide
Red coloration, usually of coastal waters, caused by large quantities of microscopic organisms (generally dinoflagellates); some red tides result in mass fish kills, others contaminate shellfish, and still others produce no toxic effects.
reef coast
A secondary coast formed by reef-building corals in tropical waters.
reef crest
Highest portion of a coral reef on the exposed seaward edge of the reef.
reef flat
Portion of a coral reef landward of the reef crest and seaward of the lagoon.
relict sediments
Sediments deposited by processes no longer active.
remote sensing
The use of airborne or satellite sensors to map Earth's surface in space and time.
reverse osmosis
The use of pressure to force water through a semi-permeable membrane, leaving behind any dissolved salts. Used to obtain freshwater from seawater.
reverse osmosis
The process of producing fresh water from seawater by forcing the water molecules through a semipermeable membrane, leaving behind salt ions and other impurities.
ria coast
A primary coast formed when rising sea level, caused by the melting of glaciers and ice sheets following the last ice age, flooded coastal river valleys.
ridge
Long, narrow elevation of the sea floor, with steep sides and irregular topography.
rift valley
Trough formed by faulting along a zone in which plates move apart and new crust is created, such as along the crest of a ridge system.
rift zone
A region where the lithosphere splits and separates allowing new crustal material to intrude into the crack or rift.
rise
Long, broad elevation that rises gently and generally smoothly from the sea floor.
Roaring Forties
Areas of ocean either side of the Equator between 40° and 50° N or S latitude, noted for high winds and rough seas.
rogue wave
A single, unusually high wave created by the constructive interference of two or more smaller waves.
rotary current
Tidal current that continually changes its direction of flow through all points of the compass during a tidal period.
rotary tide
Tide that is the result of a standing wave moving around the central node of a basin.
ROV
A Remotely Operated Vehicle- unmanned submersible controlled and powered from the surface by an umbilical cord.
salinity
A measure of the total concentration of dissolved solids in seawater, usually expressed as parts per thousand; total mass, expressed in grams, of all substances dissolved in one kilogram of seawater when all carbonate has been converted to oxide, all bromine and iodine has been replaced by chlorine, and all organic compounds have been oxidized at a temperature of 480°C.
salt budget
Balance between the rates of salt addition to and removal from a body of water.
salt marsh
An area of soft, wet land periodically covered by saltwater, in temperate zones and generally treeless with characteristic salt-tolerant plants such as reeds and samphire.
salt marsh
A relatively shallow coastal environment populated with salt-tolerant grasses. They are often found in temperate climates. They are extremely productive biologically and extend the shoreline seaward by trapping fine sediment.
scarp
Elongated and comparatively steep slope separating flat or gently sloping areas on the sea floor or on a beach.
scuba
Self-Contained Underwater Breathing Apparatus.
sea
A division of an ocean or a large body of saltwater partially enclosed by land. The term is also used for large, usually saline, lakes that lack a natural outlet.
sea cow
(dugong, manatee) Large, herbivorous marine mammal of tropical and subtropical waters.
sea smoke
Type of fog caused by dry, cold air moving over warmer water.
sea stack
Isolated mass of rock rising from the sea near a headland from which it has been separated by erosion.
sea state
Numerical or written description of the roughness of the ocean surface relative to wave height.
seamount
A steep-sided circular or elliptical projection from the seafloor that is more than ⅔ mile in height.
seasonality
The timing of major biological events cued by changes in light intensity and water temperature associated with the seasons in temperate latitudes.
secchi disk
White or white and black disk used to measure the transparency of the water by observing the depth at which the disk disappears from view.
secondary coast
A coast dominated by marine processes. See also primary coast: a coast on which terrestrial influences dominate.
sediment
A navigational instrument used to measure angles between the moon, sun, stars, and objects such as the horizon; Fine organic or material particles found in the seafloor.
seismic survey
The use of high-intensity sound waves to examine deep geological structures.
semidiurnal
Having a period of half a tidal day. East coast tides, for example, are semidiurnal, with two highs and two lows in approximately 24 hours.
semipermeable membrane
Membrane that allows some substances to pass through but restricts or prevents the passage of other substances.
set
Direction in which the current flows.
shelf sea
The shallow but often highly productive seas over continental shelves.
shingles
Flat, water-worn pebbles, or cobbles, found in beds along a beach.
shoal
Elevation of the sea bottom comprising any material except rock or coral (in which case it is a reef); may endanger surface navigation.
sideral day
Time period determined by one rotation of earth relative to a far-distant star, about four minutes shorter than the mean solar day.
side-scan sonar
High-resolution sound-imaging of the seabed.
sill
Shallow area that separates two basins from one another or a coastal bay from the adjacent ocean.
slick
Area of smooth surface water.
solar constant
Rate at which solar radiation is received on a unit surface that is perpendicular to the direction of incident radiation just outside earth's atmosphere at earth's mean distance from the sun; equal to be 2 cal/cm2/min.
sound shadow zone
Area of the ocean into which sound does not penetrate because the density structure of the water refracts the sound waves.
Southern Oscillation
Southern Oscillation is a reversal of airflow between normally low atmospheric pressure over the western Pacific and normally high pressure over the Eastern Pacific. The cause of El Niño.
specific gravity
Ratio of the density of a substance to the density of 4C water.
sphere depth
Thickness of a material spread uniformly over a smooth sphere having the same area of earth.
spicules
Small calcareous or siliceous skeletal structures found in sponges.
spit
(sand spit) Low tongue of land, or a relatively long, narrow shoal extending from the shore.
spoil
Dredged material.
sponges
Invertebrates that consist of complex aggregations of cells, bound together by protein fibers and mineral spicules.
spring tide
A tide that occurs at or near the time of a new or full moon with a large tidal rise and fall.
standing crop
Biomass present at any given time.
storm berm
See winter berm
storm center
Area of origin for surface waves generated by the wind; an intense atmospheric low-pressure system.
strait
Narrow channel of water that connects two larger bodies of water, and thus lies between two landmasses.
stratosphere
The layer of the atmosphere above the troposphere where temperature is constant or increases with altitude.
subduction zone
An area where one crustal plate is forced under another plate, giving rise to volcanic activity and earthquakes.
submersible
A small underwater vehicle designed for deep sea research and other tasks.
submersible
A research submarine, designed for manned or remote operation at great depths.
substrate
Material making up the base on which an organism lives or to which it is attached.
summer berm
A seasonal berm that is built by low energy waves during the summer and removed by high energy waves in the winter.
sun tide
Portion of the tide generated solely by the sun's tide-raising force, as distinguished as that from the moon.
supersaturation
When the concentration of a dissolved substance is higher than its normal saturation value.
surface zone
The upper layer of ocean in which temperature and salinity are relatively constant with depth. Depending on local conditions, the surface zone may reach to 1,000 meters (3,300 feet) or be absent entirely. Also called the mixed layer.
surimi
Refined fish protein that is used to form artificial crab, shrimp, and scallop meat.
symbiosis
The close beneficial feeding relationship between two species.
syzygy
Occurs twice a month, when the sun and moon are in conjunction (lined up on the same side of earth at the new moon) and when they are in opposition (on opposite sides of earth at the full moon, though usually not so directly in line as to produce and eclipse). In either case, the gravitational effects of the sun and the moon reinforce each other, and tidal range is increased.
terranes
Fragments of earth's crust bounded by faults, each fragment with a history distinct from each other fragment.
test
The shell of an organism.
thermohaline circulation
Water movement caused by differences in density produced by salinity and/or temperature changes.
tidal day
Time interval between two successive passes of the moon over a meridian, approximately 24 hours and 50 minutes.
tidal period
Elapsed time between successive high waters or successive low waters.
tide
The regular rising and falling of the sea that results from gravitational attraction of the moon, the sun, and other astronomical bodies acting upon the rotating Earth.
trade winds
Steady winds blowing east to west toward the equator to replace hot air rising from the equatorial region.
trailing margin
(passing margin) The continental margin closest to the mid-ocean ridge.
transgenic
Describing an organism that contains hereditary material from another organism incorporated into its genetic material.
transverse ridge
Ridge running at nearly right angles to main or principal ridge.
trench
A narrow, deep depression in the ocean floor, often associated with the subduction of an oceanic plate at a continental margin.
triploid
Condition in which cells have three sets of chromosomes.
trophic web
The complex feeding relationships between plants and animals in a habitat.
tropics
The zone between the Tropic of Cancer (23°27'N) and the Tropic of Capricorn (23°27'S) approximating to the area of the ocean where water temperatures remain above 69°F (20°C).
T-S diagram
Graph of temperature verses salinity on which seawater samples taken at various depths are used to describe a water mass.
tsunami
A huge wave created by earthquake or volcanic explosion. Mistakenly called a tidal wave.
typhoon
A hurricane in the western Pacific Ocean or China seas.
upwelling
The rising of deep, cold-nutrient-laden waters into the surface layers, close to continental coasts
vanishing tide
A mixed tide of considerable inequality in the two highs or two lows so that the "high low" may become indistinguishable from the "low high". The result is a vanishing tide, where no significant difference is apparent.
water budget
Balance between the rates of water added and lost in an area.
wave
The disturbance in water caused by the movement of energy through the water.
wave period
The time it takes for successive wave crests to pass a fixed point.
wave ray
Line indicating the direction waves travel; drawn at right angles to the wave's crest.
West Wind Drift
The current driven by powerful westerly winds north of Antarctica. The largest of all ocean currents, continues permanently eastward without changing direction. See Antarctic Circumpolar Current: The current driven by powerful westerly winds north of Antarctica. The largest of all ocean currents, it continues permanently eastward without changing direction.
westward intensification
The increase in the speed of geostrophic currents as they pass along the western boundary of an ocean basin.
Wilson, John Tuzo
(1908-1993) Canadian geophysicist who proposed the theory of plate tectonics in 1965.
wind
The mass movement of air.
wind duration
The length of time the wind blows over the ocean surface, a factor in wind wave development.
wind strength
Average speed of the wind, a factor in wind wave development.
wind wave
Gravity wave formed by transfer of wind energy into water. Wavelengths from 60 to 150 meters (200 to 500 feet) are most common in the open ocean.
wind-induced vertical circulation
Vertical movement in surface water (upwelling or downwelling) caused by wind.
winter berm
A relatively permanent berm that is formed by high energy waves in the winter.
world ocean
The great body of saline water that covers 70.78% of Earth's surface.
xanthophyll
A yellow or brown accessory pigment that gives some marine autotrophs a yellow or brown appearance.
zenith
Point in the sky that is immediately overhead.
zero velocity surface
A reference level at which the horizontal velocities are thought to be practically zero.
zone
Division or province of the ocean with homgeneous characteristics.
zooanthellae
Single-celled photosynthetic organisms that live in coral tissues in a symbiotic relationship.
zooplankton
One of the two groups into which plankton are divided, the other being phytoplankton. Zooplankton are a large group of micro- and macroscopic animals ranging in size from a fraction of a millimeter to 30-50 millimeters; Small animals that spend all or part of their life cycles floating in the surfaces layers of the ocean.
zooplankton
Animal members of the plankton community.
zooxanthellae
Unicellular dinoflagellates that are symbiotic with coral and produce the relatively high pH and some of the enzymes essential for rapid calcium-carbonate deposition in coral reefs.
Zulu time
Solar time along the prime meridian passing through Greenwich, England; also known as the Greenwich Mean Time (GMT) or Universal Time.
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